A mantra I know is "Om anichi marishiei sowaka". If memory serves me correctly it is the invocation of Marishiten, the Warrior Goddess that chases away devils. Ninja tend to use this in their meditations when the use the Daikongorin-in mudra or the Touken sword mudra of Fudou the Immovable One. Yes, except I am familiar with it being "on anichiya marishiei sowaka" and is indeed a mantra for Marishiten. However, I believe that is the "Invisibility" or "Hidden Form" mantra, and so would use that mudra instead of the mudra you described (which is also a valid mudra for marishiten).

禹 步 法 ： 前 舉 左 ， 右 過 左 ， 左 就 右 。次 舉 右 ， 左 過 右 ， 右 就 左 。 次 舉 右 ， 右 過 左， 左 就 右 。 "Method of the Pace of Yu: First lift (and step forward with) the left foot, then have the right foot pass the left, and finally have the left foot come (in line with) the right. Next, step forward with the right foot, then have the left foot pass the right, and finally have the right foot come in line with the left. Next, step forward with the left foot, then have the right foot pass the left, and finally have the left foot come in line with the right."

Oringally, the Pace of Yu was a secret method used to avoid negative spirits and influences (魔), purify the heart/mind and body, and obtain power from the Divine Immortals to boost your own abilities. Therefore, Daoist priests (道士) always walk to the Pace of Yu before using magical skills or spiritual practices (note: this comes from the source Jujutsu: Reifu no Higi Hiden, but I think it might be somewhat misleading. There are now several different versions of the Pace of Yu and literally hundreds of Star Stepping patterns in Daoism. It is true, however, that several magical formulas in the Mawangdui Medical Manuscripts begin with performing the Pace of Yu and some form of ritual stepping pattern is often used in the initial part of Daoist rituals and ceremonies or when sending the spiritual petition to the deities.). It is said that the journey of one-thousand li begins with a single step (see Daodejing ch. 64). Surely this comes from the idea that the first step itself is correcting the heart/mind and cleansing the body of impurities. For, if you are not in this state then you will not align with the principles of Heaven (天理).

The footprints of the Pace of Yu seem to form the shape of the seven stars of the Big Dipper/Northern Dipper (北斗七星 jp. hokuto shichisei) and the two "hidden" guardian stars, which has led to association of the Pace of Yu to Pacing the Big Dipper. This also corresponds to the Nine Heavens. So, performing the Pace of Yu can symbolize flying over the Nine Heavens and delivering petitions and reports to the deities. Also, the number of toes left in the footprints is the same as a sacred number that corresponds to Heaven and Earth, among other things. There are various other theories attached to the correspondences of the Pace of Yu as well. Putting aside any specialized knowledge, two important points to keep in mind before practicing the Pace of Yu is that it will release you of tension and act as an expedient method for exercising the maximum potential of your abilities to reach success.

Some may be inclined to believe this sets up a magical barrier or kekkai 結界. This is not the case. It may have properties of clearing obstructions, purifying yourself, and warding off demons, but it does not set up a magical barrier proper. Rather, it is foremost a method that allows you to advance through the spirit world 霊界 (reikai) or the various Heavens.

Now on to the practice. To be specific, this version of the Pace of Yu is called "Thee Paces and Nine Traces" 三歩九跡. First stand with feet about shoulder width with feet parallel and toes pointing forward. Then take a half step forward with the right foot, and then a half step backward with the left foot. This is the "Upright Stance of the Pace of Yu" 禹歩正立. The rest follows the method outlined in the Baopuzi. First step forward with the left foot, then step forward with the right foot while passing the left, and finally step the left foot forward so it is even with the right. These three steps complete the first pace. The second pace has the right foot step forward, then the left foot stepping ahead of the right, and finally the right foot stepping even with the left. The third pace repeats the pattern of the first pace. Please click on the thumbnail below to see a diagram of the Pace of Yu of the Three Paces and Nine Traces.


Source: Jujuts: Reifu no Higi Hiden

After having looked at the diagram, I would like to introduce another important symbolic correspondence of this Pace of Yu. This version of the Pace of Yu can be interpreted as placing the trigram Kǎn 坎 (Water) ☵ over the trigram Lí 離 (Fire) ☲. Reading from left to right it could be seen as the following, |¦|¦|¦. If you divide the Pace of Yu in six levels, then you will see there are levels where you left a single step and levels where you stepped with both feet. Where you stepped with one foot is given a solid yang/positive line since one is an odd number. Where you stepped with both feet is given a broken yin/negative line since it is an even number. Here the trigrams Kan and Li formed by the Steps form an ideal shape that has attained a natural balance of Yin and Yang 陰陽.

Essential points to be aware of when practicing are to regulate the breath and to practice with the same feeling as meditation. You can treat this practice as a walking meditation.

Additionally, there are practices where you recite the incantation of the Kuji (九字) while conducting the Pace of Yu. The version of the Kuji to be used here is the original version found in the Baopuzi, aslo known as the "Secret Invocation of the Six Jia" 六甲秘祝. 臨 兵 鬥 者 ， 皆 陣 列 前 行 or in its Japanese variants 臨、兵、闘、者、皆、陣、列、前、行 (only one character is written differently, but it means the same thing). With each step you recite one of the words. In Japanese you would pronounce it as "Rin, Pyou, Tou, Sha, Kai, Jin, Retsu, Zen, Kou!" With the final "kou!" you want to put a little extra spirit, or "umph" into it. Depending on the situation you may also recite the incantation silently or quietly. Here's the pinyin in case you are interested in the Chinese version, "lín bīng dòu zhě jiē zhèn liè qián xíng." It doesn't matter if you do it in Chinese or Japanese. Japanese is easier to pronounce if you aren't acquainted with Chinese. If you are curious as to what the incantation means, here is my translation, "Soldiers who can face (the enemy), warriors. They all form a row (battle formation) and move out before me!" In this context, do not use the later form of the Kuji that got changed around once it was transmitted to the Tantric Buddhist sects. That is the more popular form of Kuji that goes 臨兵闘者皆陣烈在前 (Rin, Byou, Tou, Sha, Kai, Jin, Retsu, Zai, Zen). Go ahead and practice the mudras with this later form, but not with the Pace of Yu. Besides the fact that my sources specify the older version found in the Baopuzi I feel the older version is more in line with a Daoist practice like the Pace of Yu, and also I think it is possible that the older version is more appropriate since it ends with the character 行 (kou) which can mean "to go; to travel" and the Pace of Yu involves walking forward and has traditionally been used in magical techniques related to travel. The later form ends with 在前 (zai zen) which indicates "(they are) before me" which has a more static feel in my opinion. I may speak more on the Kuji later, but it is not something I really feel like writing a discourse on. There are various versions and teachings on the Kuji, and there is also a version seemingly particular to Onmyoudou that most people in the English speaking world are not aware of.

There is also the practice of reciting the Nine Heavens, which correspond to the Seven Stars of the Big Dipper and the two hidden guardian stars. Here is the order of the Heavens and their corresponding star in pinyin and Japanese in parentheses (note that for the second Heaven the Japanese use a different character, otherwise it corresponds nicely to the Chinese names):
天逢 tiān féng (tenpou) - 右弼 yòu bì (yuu hitsu)
天芮 tiān ruì (天内 tennai) - 左輔 zuǒ fǔ (sa ho)
天衝 (天沖) tiān chōng (tenshou) - 破軍 pò jūn (hagun)
天輔 tiān fǔ (tenpa) - 武曲 wǔ qǔ (mugoku)
天禽 tiān qín (tenkin) - 廉貞 lián zhēn (renjou)
天心 tiān xīn (tenshin) - 文曲 wén qǔ (mongoku)
天柱 tiān zhù (tenchuu) - 祿存 lù cún (rokuzon)
天任 tiān rèn (tennin) - 巨門 jù mén (komon)
天英 tiān yīng (tenei) - 貪狼 tān láng (tonrou)

Here is another correspondence table drawn fromthe 『五行大義』section of the 『遁甲経』
(sorry, but please compare the characters below to those above, they are in the same order)
(I translated 神 as "kami" here but "god", "deity", or "spirit" may be just as appropriate if not more so)

天逢　破軍星　木神 (wood kami)
天内　破軍星　水神 (water kami)
天衝　破軍星　金神 (metal kami)
天輔　武曲星　土神 (earth kami)
天禽　廉貞星　火神 (fire kami)
天心　文曲星　木神 (wood kami)
天柱　祿存星　水神 (water kami)
天任　巨門星　金神 (metal kami)
天英　貪狼星　土神 (earth kami)
Curiously the two hidden stars are left out and 破軍星 (hagun shou) is used three times. Also of note is the reverse of the Creation Cycle (i.e. wood is produced by water is produced by metal is produced by earth…). Also interesting is it starts with Wood which could correspond to growth and ends with Earth which could correspond to balance and stability. I have seen other correspondences for the phases and the Seven Stars, but this seems good in this context.

For ease of use, if you wanted to recite the name of the Nine Heavens in Japanese as you perform the Pace of Yu see the following: 天逢、天内、天衝、天輔、天禽、天心、天柱、天任、天英 Tenpou, Tennai, Tenshou, Tenpa, Tenkin, Tenshin, Tenchuu, Tennin, Tenei.

Feel free to experiment and figure out what works best for you, but I will give you a few suggestions to try. The following paragraph is from my own experimentation and ideas, so it does not draw from any source in particular. First start by regulating the body. As for the posture, keep the knees slightly bend, tuck in the hips slightly to help straighten the back, roll the shoulders back and relax them so they sit naturally, and tuck in the chin slightly and push up with the top of the skull to open up the space where the spine meets the skull. Relax the muscles and joints and feel the alignment of the body. The spine should be straight and long (to get the feeling of the posture you may wish to stand with your back to the wall a few times). Your arms may hang relaxed at your sides, palms facing down with fingertips forward at waist level, or maybe in the attitude of prayer in front of your chest. Lightly close the mouth and touch the tip of the tongue to the upper palette. In the initial centering and grounding you may have your eyes closed with the gaze either at 45-degrees down or at the tip of the nose with the awareness of your gaze focused inwardly. Once you practice the Pace of Yu open the eyes for a relaxed, unfocused gaze straight ahead. Unfocused in that you are not focused on any particular point, but rather aware of everything in the field of your vision. Focus your awareness to the soles of the feet (if you like, focus on the center of the soles called the "Bubbling Well") and sink your awareness into the bottomless Qi (氣 jp. Ki) of Earth. Then draw your awareness up through your legs, through your entire body, and up to the crown of the head. Then through the crown of the head become aware of the vast, limitless Qi of Heaven. Feel yourself acting as a conduit of the energy of Heaven and Earth. This is not some sort of body scan or visualization practice. Use your awareness to sense the energies of Heaven and Earth and the energies of your own body. You want to work at having simultaneous awareness of your body, the Earth below, and Heaven above. This is more about using your awareness tactilely to sense. You may naturally "visualize" something while doing this, but it is not to be the focus here. Inhale and exhale through the nose. The breath should be long, deep, smooth, and quiet. Do not force it, and trust in the wisdom of the body. Regulate the breath with the expansion and contraction of the lower abdomen (lower dantian 丹田 jp. tanden). Do not think about sucking in or expelling air with the nose, but let it open and close naturally as a passageway for the Vital Breath. I would recommend starting with natural breathing (expand the lower abdomen on the inhale and contract on the exhale), but if you know Daoist/Reverse Breathing then you may experiment with that as well. If you have not received any instruction on reverse breathing, then do not worry about it for now. You can try inhaling right before each Pace and exhaling through the course of stepping. The mind should be still. Absorb your awareness in the practice of the Pace of Yu. If other thoughts come up let it come and let it pass away. Do not push thoughts away and do not follow trains of thought. Embody the technique (in this case, the Pace of Yu). You may wish to lightly tap the teeth together 36 times with the lips lightly closed before initiating the formal practice. This is a typical Daoist technique used that can stimulate the teeth and gums and send gentle vibrations through the head. Afterward you may practice swallowing the saliva according to the Daoist practices if you know how. I have probably found my best results with a continuous flow of movement. That is, not pausing at each step or after each pace. So, I would inhale in the initial stance, shift my weight to my right as I step forward with the left and begin my exhale, then shift my weight to the left as I step with the right, and shift to the right as I step up with the left, then inhale as I am shifting my weight to the left for the second pace and begin my exhale as I step down with the right foot, and so forth. I do it relatively slow and treat it like a qigong exercise. Pay attention to the shifting of weight. This in itself is an interplay of Yin and Yang with the emptying and filling of weight to the legs. When inhaling you can draw energy into your body from the Earth, and as you exhale draw down celestial energy from Heaven to the Earth where it forms a Trace. You may wish to visualize the Traces form centers of energy and that at the end they are connected similar to a constellation (like a Dipper constellation) and maybe you would like to visualize the Kan and Li trigrams superimposed.

Fun Trivia:
-In episode eight of the TV anime adaptation of Shōnen Onmyōji (少年陰陽師), the main character Abe no Masahiro (安倍昌浩) walks the Pace of Yu while reciting the names of the Nine Heavens.

-In episode one of the TV anime adaptation of the game Tokyo Majin Gakuen Kenpuchō (東京魔人學園剣風帖), Tokyo Majin Gakuen Kenpuchō: Tō (東京魔人學園剣風帖 龖), one of the Chinese characters recites 福寿光無量 (fuku ju kou mu ryou) and then traces the pattern of the Big Dipper while reciting 臨、兵、闘、者、皆、陣、列、前、行 (rin, pyou, tou, sha, kai, jin, retsu, zen, kou!). This seems to be based on the idea of a star stepping pattern in conjunction with the Secret Invocation of the Six Jia (the Kuji).

References:

"Finger Gestures and Pacing the Big Dipper." 26 Jun. 2008. 08 Aug. 2009. <http://eng.taoism.org.hk/religious-activities-rituals/talismans-registers-magic-skills/pg4-3-3.htm>.

Fujimaki, Kazuho 藤巻一保. Abe no Seimei Senjutsu Taizen 『安倍晴明占術大全』. Tokyo: GAKKEN, 2000.
-The title reads "Encyclopedia of Abe no Seimei's Divinatory Techniques." It is primarily a modern translation of The Collected Works of the Golden Crow and the Jade Rabbit along with some supplementary material on Onmyoudou magic and ritual.

Harper, Donald J. Early Chinese Medical Literature. New York: Kegan Paul International, 1998.

"Henbai Sahou 反閇作法." 07 May 2005. 08 Aug. 2009. <http://www7a.biglobe.ne.jp/~jirihon/juhou/henbai.html>.

"Kekkai, Shugorei, Kuji no koto ni tsuite 結界・守護霊・九字のことについて." 12 Jun. 2009. 12 Jun. 2009. <http://charm.ten.thebbs.jp/1079085769/>.
-a Japanese bbs which I referenced some posts from. The title means "Concerning Magical Barriers, Guardian Spirits, and the Kuji."

Ōmiya, Shirou 大宮司郎. Jujutsu: Reifu no Higi Hiden 『呪術・霊符の秘儀秘伝』. Tokyo: BNP, 2000.
-Title reads "Magic: The Secret Rituals and Transmissions of Spirit Talismans." Much of the information in this article is paraphrased from this source, rearranged, and supplemented with information from other sources. A good entry level book that covers many essential skills for East Asian, and particularly Japanese magic, with an emphasis on Chinese/Daoist style paper talismans. It is not a deep book, but good books for general readership on this type of subject aren't all that common in East Asia in comparison to the state of Western published works on the occult. Though they all appear Chinese/Daoist style, some may be developed in Japan using the Daoist style of talisman writing.

Toyoshima, Yasukuni 豊島泰国. "Onmyoudou-kei no Jujutsu 陰陽道系の呪術." Nihon Jujutsu Zensho 『日本呪術全書』. Tokyo: Harashobo, 2007.
-Article title reads "The Onmyoudou System of Magic." The title of the books reads, "The Complete Book of Japanese Magic."

Wong, Eva. Nourishing the Essence of Life. Boston: Shambhala, 2004.

Wu, Heng Sheng 吳恆昇. "Baopuzi Neipian Jiaoshi Juan 11-20 抱朴子內篇校釋 卷11-20." 01 Oct. 2004. 08 Aug. 2009. <http://www.chinapage.com/big5/literature/bp02.htm>.

I remember seeing this on that show and at the time i was wondering what it was, thanks for this information.