What it does
Replicate lets you pay a spell's mana cost any number of additional times as you cast it. For each time you pay, you copy the spell. If it targets, you choose new targets for each copy independently, so you can spread effects around or pile them onto one thing.
The key nuance: replicate is paid and copies are created as you cast the spell, while it's still on the stack—not when it resolves. The copies are created directly on the stack and don't get "cast," so they won't trigger cast-related abilities (like "whenever you cast an instant"). They will, however, trigger abilities that care about spells resolving or copies. Also, you can't replicate a spell unless you actually cast it.
In Commander, replicate shines as scalable removal or burn (think Shock-style effects hitting multiple creatures), turning excess mana into a flexible, multi-target payoff.













