What it does
A creature with double strike deals its combat damage twice: once during the first combat damage step (alongside first strike creatures), and again during the regular combat damage step. So a 4/4 with double strike deals 8 total damage if unblocked.
The most common misconception is that double strike "doubles" damage like a multiplier—it doesn't. It deals damage in two separate steps, which matters for things like lifelink (you gain life twice), trample (excess is recalculated each step), and deathtouch (a single point in the first step can kill a blocker, letting all regular-step damage trample through). If a blocker dies to first-strike damage, the second hit goes nowhere unless the creature has trample.
In Commander, double strike is a premier wincon on voltron and combat-damage-trigger builds—it effectively halves the commander damage threshold (10 hits instead of 21) and stacks brutally with +1/+1 buffs and infect.













