When an allied Pokémon faints in battle, a Pokémon with Receiver as its Ability will gain the fainted Pokémon's Ability in place of its own. When this happens, the new Ability activates immediately, as if it had just entered the battle.

Shedinja can Life Orb + Shadow Sneak which will KO him then he can give Wonder Guard to Passimian which will grant him 15 immunities. You can thank me for pointing out that this is a thing