Saheeli, Radiant Creator

Every artifact or Artificer you cast banks a counter, and three of them, spent once per combat, buys a hasty 5/5 clone of anything you control. That combat-step timing is the whole trick: the copy resolves before attacks are declared, so it swings the same turn it arrives, and you can point it at something already tapped without caring that the original is committed elsewhere. The clone template does the heavy lifting. It copies a permanent's abilities, staples on a 5/5 artifact-creature body and haste, and sets the token to die at the next end step, so the payoff lives in the enter-the-battlefield or attack triggers you harvest for one turn rather than in a board that sticks around. Aim it at a permanent whose entry or activation is the entire reward and the sacrifice clause becomes irrelevant: the token has already done its work before it leaves. What keeps the engine honest is the counter arithmetic. Three energy per activation against one energy per qualifying spell means the deck has to be genuinely artifact-dense before the clone comes online every combat rather than once every few turns; the sink outpaces the source unless you build to feed it. The design's real ambition is turning energy, usually a resource that sits inert until a burst payoff, into a repeatable per-turn value spigot, provided you supply the cast triggers to keep it filled.