Ability · Gen 5 · 4 Pokémon
Illusion
This Pokemon appears as the last Pokemon in the party until it takes direct damage.
When this Pokemon switches in, it appears as the last unfainted Pokemon in its party until it takes direct damage from another Pokemon's attack. This Pokemon's actual level and HP are displayed instead of those of the mimicked Pokemon.
Illusion was introduced in Generation 5. 4 Pokémon and forms can have it.
Best Pokémon with Illusion
Ranked by usage in public Pokémon Showdown battles (Champions VGC first, then National Dex OU, SV OU and Champions Singles), with how many of each Pokémon's sets actually run Illusion.
Pokémon with Illusion
As a regular ability (4)
Zorua
Hisuian ZoruaIllusion FAQ
What does Illusion do?
When this Pokemon switches in, it appears as the last unfainted Pokemon in its party until it takes direct damage from another Pokemon's attack. This Pokemon's actual level and HP are displayed instead of those of the mimicked Pokemon.
Which Pokémon have Illusion?
4 Pokémon and forms can have Illusion: Zorua, Hisuian Zorua, Zoroark and Hisuian Zoroark.
What are the best Pokémon with Illusion?
By competitive usage, the most used Pokémon that can have Illusion are Hisuian Zoroark (#97 in Champions VGC, 100% run Illusion) and Zoroark (#246 in Champions VGC, 100% run Illusion).
Effect text from Pokémon Showdown (MIT); which Pokémon have it from Showdown's Pokédex, cross-checked against PokéAPI. Unofficial fan site.