What it does
Berserk triggers when damage from an opponent's move specifically causes Drampa's HP to cross from above half to below half. That trigger grants +1 Special Attack. Passive damage sources — poison, burn, weather chip — do not trigger it. Each crossing of the 50% threshold triggers it once; further drops below half in subsequent turns do not re-trigger it.
Who runs it
Drampa is the carrier at 9% usage. Normal/Dragon, 135 base Special Attack, 45 base Speed. It is slow and moderately bulky. Berserk builds on top of that 135 Special Attack: the +1 stage brings effective Special Attack to around 1.5× the base value, pushing output well into threatening territory against anything that doesn't resist.
How to use it
Berserk can trigger reactively (opponent lands a hit that crosses the threshold) or actively by pairing with an Weakness Policy. The Weakness Policy combination is the classic setup: a super-effective hit that drops Drampa below half triggers both the Weakness Policy (+2 Special Attack) and Berserk (+1 Special Attack) simultaneously, landing on +3 Special Attack. With 135 base Special Attack as the foundation, that is a massive damage output spike. Trick Room support is essentially required since Drampa's 45 base Speed means it moves last in normal conditions.
Tips & strategy
The 9% usage rate is honest about the risk. Once Drampa is below half HP, one more solid hit ends it before it gets to fire off the boosted attack. Keeping it alive to actually use the boost requires either defensive support or a situation where it can immediately fire off its enhanced Special Attack. Trick Room teams give Drampa a consistent window to move first. The Weakness Policy setup is high-variance — if the super-effective hit doesn't arrive in the right timing, or if it KOs Drampa outright, the entire setup collapses. Build around a partner that can take pressure off Drampa after the boost triggers.