What it does
Quiver Dance raises Special Attack, Special Defense, and Speed by one stage each in a single turn. That density is the point — Swords Dance gives a bigger Attack jump at +2, but Quiver Dance moves three different numbers at once, and the combination of Speed and SpDef together changes what the opponent can do in response.
After one Quiver Dance: the Speed jump means you outspeed most unboosted targets you couldn't before. The SpAtk jump means moves that were hitting for 60% are now hitting for 90%. The SpDef jump makes it genuinely harder for the opponent to revenge KO you with a resisted special hit — something that would have 2HKO'd before might only deal around 65% now.
Who runs it
Volcarona at 45% usage is the primary carrier. Its Special Attack base is already strong, and after one Quiver Dance it moves into a range where its Fire-type and Bug-type STAB moves threaten KOs on a wide range of targets. The Speed boost cements its ability to move first, and the SpDef boost makes it harder to interrupt before the next turn's attack.
How to use it
You need one safe turn. In doubles, the clean options are: use Protect the same turn your partner removes the immediate threat, or catch the opponent on a turn they're using a field move. One Quiver Dance is usually all you need — after that, the Speed and SpAtk boosts together make Volcarona genuinely difficult to deal with.
Watch out for Trick Room. Quiver Dance Speed boosts become a liability under Trick Room because higher Speed means you move last. If you see a Trick Room setup being threatened, you need to either prevent the room or hold off on boosting Speed until it expires.
Tips & strategy
The SpDef boost is easy to underestimate. It doesn't just help Volcarona survive — it makes the opponent's damage calc less clean, which buys you the second attack turn you need to finish the job.
Rock-type physical moves are the biggest threat after a Quiver Dance. The SpDef boost does nothing against physical damage, and Rock hits Volcarona for 4×. Scan the field before you commit the Quiver Dance turn — if a Rock-type physical attacker is on the field and healthy, that's the thing to deal with first.