False Dragon Titan boss battle swerves players by bringing in the massive Dondozo for the first stage of the battle, only to reveal that the real Dragon Titan is the tiny Tatsugiri.

Source: https://gamerant.com/pokemon-scarlet-violet-how-to-use-tatsugiris-commander-ability/

This Ability activates when both monsters are on the field, allowing Tatsugiri to go inside Dondozo's mouth, preventing it from taking damage for the turn and boosting all of Dondozo's stats by two stages.

Source: https://gamerant.com/pokemon-scarlet-violet-dondozo-tatsugiri-competitive-vgc-doubles-meta/