What it does
Rock-type moves hit 20% harder. No HP cost, no lock. Coverage moves outside Rock get nothing.
Who runs it
Rampardos at 20% is the textbook case. Its base Attack is 165 — among the highest in the game — but its defenses and HP are shaky. Life Orb's 10% recoil per hit is a genuine threat: take two hits from the opponent plus two Life Orb triggers, and Rampardos is gone before it's done its job. Hard Stone preserves that fragile HP pool while keeping Rock damage elevated.
Rhyperior at 31% has different reasoning: it's slow, meaning it typically eats a hit before attacking. Life Orb on top of that chip damage can push Rhyperior into KO range prematurely. Hard Stone eliminates that variable. Aggron at 15% has numerous type weaknesses; Tyrantrum at 14% wants to stay alive long enough to fire multiple strong hits.
How to use it
Rock attackers primarily use Stone Edge or Rock Slide. In doubles, Rock Slide hits both opponents — Hard Stone applies to both hits simultaneously, making it especially efficient in doubles formats. Focus on trading well rather than tracking Life Orb thresholds.
Tips & strategy
Rock Slide's spread attack value in doubles is a core Rock-type strategy. Hard Stone amplifies both targets at once, and Rock Slide's higher accuracy vs Stone Edge makes the combination more consistent.
For Rampardos specifically: if it's only going to get 2-3 attacks before it's KO'd, Life Orb's 10% extra damage per hit comes with 20-30% HP cost. The math of whether that extra damage trades positively depends on how much extra damage it converts into KOs. Often it doesn't — Hard Stone is the safer bet.