What it does
Kebia Berry triggers automatically when the holder takes super-effective Poison-type damage, halving it, then is consumed. Only fires on super-effective Poison moves.
Poison hits Fairy and Grass types for super-effective damage. Fairy is one of the densest defensive typings in the current meta, and Poison moves like Sludge Bomb and Sludge Wave deal serious special damage to Fairy types — often enough to threaten a KO or force a dangerous range. The berry buys the one turn of safety you need.
Who runs it
Aromatisse (14% of sets) leads the pack — pure Fairy, obvious Poison weakness, and it wants to stay on the field running support long enough to actually do something. Alcremie (10%) is the same story. Hydrapple (9%) is Grass/Dragon, double-weak to Poison, and special Poison moves are one of its main threats. Tsareena (5%) and Serperior (3%) are Grass types with the same structural vulnerability. Primarina (3%) is Water/Fairy with a Poison weakness. Clefable (3%) and Gardevoir (1%) round out the Fairy side.
What all of these share: they're weak to Poison, and their roles — support, field control, special offense — all require at least one extra turn to actually matter.
How to use it
Kebia Berry shines when you know the Poison attacker is going to swing at your Fairy or Grass type this turn. If you can Protect to dodge, sometimes that's the right call — but if you need to act, the berry lets you stay in and do your job. Sludge Wave is particularly relevant because it hits both your Pokémon simultaneously — you can't dodge one hit without protecting both.
Vs. Focus Sash: many Fairy types have solid Special Defense, which means Kebia Berry can leave you at genuinely usable HP, not 1 HP. For a support Fairy that needs to keep functioning, that surviving HP margin is usually more valuable.
Tips & strategy
The two relevant Poison moves behave differently: Sludge Bomb is single-target, which means your other Pokémon is unaffected; Sludge Wave hits both of your field slots. When you see a Poison-type threat in team preview, factor in which move they're likely carrying — it changes how you position both your Pokémon that turn.