Shaun, Father of Synths

Populate-adjacent token generation has a familiar shape: pick a permanent, stamp out a copy, watch the board double. This one narrows the aperture to something stranger. It copies only attacking legendary creatures, only when you attack, and only one target per combat, minting that copy already tapped and swinging. That single restriction converts a value engine into a combat trick with a body attached, and it rewards the exact deckbuilding choice most token strategies avoid: loading up on legends. The copy that arrives mid-swing is not a legion but a single extra threat, chosen from among your unique attackers, and the payoff scales with how good your best legendary attacker is rather than how wide the board runs. Note the timing wrinkle: because the token is created already tapped and attacking, it skips the declare-attackers step entirely, so "whenever this creature attacks" triggers never fire off the copy. What you want to duplicate is a body whose value lives in raw stats, evasion, or a static ability, not one whose payoff hangs on entering combat under its own power. The catch lives in the leaves-battlefield clause: the Synth tokens are tethered to their source, so removing the 3/4 exiles the copies rather than merely stranding them. That is the balancing work, keeping the extra attackers from outliving the engine that made them, and it means the whole plan folds if an opponent answers the body at the right moment. What you get is a payoff that relocates board expansion from the end step to the declaration of attackers, and asks you to commit to legendary creatures as a subtheme rather than a scattering of good cards.