Seimon

Holy Gate (せいもん) is a summoning technique developed fifty years before the warring states period to call upon the power of three different yōkai. Because of its power it has been re-classificated to kinjutsuduring the foundation of Mangetsugakure.

Overview
When the user learns the technique a tattoo with the kanji 門 (gate) appears on his back. This is the portal that allows the yōkai to leave their world and enter ours. While on our world, the yōkai learns the shinobi orders telepathically and must obey. However, if the will of the shinobi weakens the yōkai might rebel itself and destroy everything in its path.

When the three of them are together they are strong enough to destroy a small country. However, summon more than one yōkai at the same time can be dangerous since the more are summoned the more difficult are to control.

If the user dies during the jutsu, the yōkai are automatically sent back to their world and the kanji on the user's back disappears.

History
Many shinobi has lost their lives trying to master it, few others has lost it by over using its power, that why this is a forbidden jutsu.

While its true origin is uncertain, the scroll that contains these techniques has always been guarded by the monks of Gattenshi Tera. However, at some point, Tenzen managed to steal it and master it.

Reference
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