Tranquilize is an ability newly introduced in Pokémon Mind x Matter.
When the bearer is hit by a move that makes contact, there is a 30% chance that the attacking Pokémon will fall asleep.
If a Pokémon with this Ability is hit by a multi-strike move that makes contact (such as Fury Swipes), each hit has an independent chance to activate this Ability.
Pokemon MxM has a permanent sleep clause.
Outside of Battle
The Tranquilize ability has no effect in the over-world.
"Contact with the Pokémon may induce sleep"