The Peregrine Dynamo

Copy effects usually anchor to spells: a Fork, a Twincast, something that grabs a spell off the stack. This one anchors to abilities instead, and the restriction is where the whole design lives. It targets an activated or triggered ability from a legendary source you control, and specifically not from your commander, which quietly walls off the most obvious loop the card would otherwise enable. What is left is a machine for doubling the constellation of legendary permanents that already populate a certain kind of deck: the tap-for-value abilities, the enter-the-battlefield triggers, the once-per-turn engine outputs that legends tend to carry. The 1/5 body is a defensive shell, not a clock, and the haste is there so the copy engine can come online the turn it lands rather than waiting a rotation for summoning sickness to clear. The real subtlety is that it copies triggered abilities too, not just activated ones: when a legendary permanent triggers, this can stack a second instance of that same trigger alongside it, new targets and all. That folds it into a payoff for any strategy already built around legendary sources, turning a board of one-of-a-kind permanents into a board that fires twice.