What it does
Opportunist fires whenever an opponent's stat stage actively increases — Attack, Special Attack, Defense, Special Defense, or Speed. The holder copies that same increase instantly. If the opponent uses Swords Dance for +2 Attack, the Opportunist user also gets +2 Attack for free. If they use Nasty Plot for +2 Special Attack, same deal.
The trigger requires an active stat boost from the opponent. Stat drops the opponent inflicts on others don't count. Your own stat boosts don't trigger this either. The key condition is 'opponent's own stat goes up'.
The effect is punishing setup: every turn your opponent spends building stats, you get the same benefit without spending your own action. A Swords Dance meant to set up a sweeper effectively doubles its cost.
Who runs it
Espathra has a 1% Opportunist usage rate. The other 99% run different abilities. Espathra's main alternative is Speed Boost, which raises Speed every turn automatically — that's unconditional value regardless of what the opponent is doing. Opportunist requires the opponent to cooperate.
The theoretical use case is a fast Pokémon with offensive power that can immediately convert copied stat boosts into damage. Espathra fits that profile, but Opportunist only makes that combination relevant against setup-heavy opponents.
How to use it
There's no active play with Opportunist. You switch in or lead, and wait. If the opponent uses a boosting move, you get the same boost and immediately plan how to use that new power — an unexpected Attack boost from the opponent's Swords Dance might let you KO something you otherwise couldn't.
Against teams with zero setup moves — pure status/weather/chip damage strategies — Opportunist contributes nothing the entire game. That's why the usage rate is at 1%.
When it does hit the right matchup (opposing Swords Dance, Dragon Dance, Calm Mind users), Opportunist is a hard counter to the setup turn. One turn where the opponent tries to build and you skip the entire setup process.
Tips & strategy
Opportunist and Swagger have an interesting interaction: Swagger forces the target's Attack up by +2 while confusing them. If that target has Opportunist, they get the +2 Attack — but are also confused. Whether that trade works depends on context.
Opportunist is a BO1 meta-read ability. In prepared best-of-three where you know the matchup, it can be powerful. In general play where you can't guarantee the opponent is running setup sweepers, the more consistent abilities pull ahead.