Kirisame
It is used by Mist Village ANBU ninjas.
It causes it to begin raining, however it's a special rain that drains the chakra from whatever it touches.
However this rain does not drain chakra from people, only techniques making it impossible for jutsus to be performed while
this is active. This goes for both the user and anyone else in the area though with practice the rain can be 'localized' to affect a smaller area.
For implementation in the game I would suggest a constant seal(In the anime it is performed with one seal) like ikioidzuku with the only difference being that after you stop performing the technique the rain continues to fall until the end of the tick (Takes a while for the rain to finish hitting the ground etc) and it would have a constant chakra cost like kirgakure.
This would obviously be a specialized technique, possibly (-S-) type that requires a quest or series of quests to learn and it's application would be mostly limited to group style combat.
Just my idea