In Magic, double is a keyword action that makes a number twice as large. When an effect tells you to double something—like damage, counters, or the effect of another doubling effect—you take the current amount and add that same amount again. For example, if you double an effect that doubles damage, it quadruples the damage instead. Double strike is a related keyword ability: a creature with double strike deals combat damage both during the first-strike damage step and during the regular combat damage step.
Doubling effects are powerful because they scale with what you already have. The bigger your creature’s power or the more counters on a permanent, the more you gain from doubling. Double strike makes a creature extremely dangerous in combat, often letting it deal lethal damage before the opponent can strike back. These abilities reward building up a strong board presence.
