Sandstorm Crasher

Exert is a keyword built around a delayed cost: push harder now, pay by staying tapped through your next turn. What this creature does with that window is more ambitious than the usual "get bigger this combat" template. The exert trigger stamps out a tapped and attacking copy of a creature you control, then sacrifices it at the next end step. That token is a fresh permanent entering the battlefield, so every enters-the-battlefield effect the copied creature carries fires again. Note the target line: it says "creature you control," which includes this creature itself, so in a pinch it can clone its own trampling body for a doubled swing. But the copy earns its keep when you aim it elsewhere: point it at a value engine with an enter-the-battlefield trigger and you get that effect a second time each turn a token is made. The catch is specific: exerting locks this one down for a full rotation, so the copy has to justify a turn of the attacker's absence, and the token vanishes at end step regardless of what it accomplished. That end-step sacrifice cuts both ways; if you have a sacrifice outlet, the token is fodder you get to spend on your own terms before it disappears anyway. Left alone it is a 3/4 trampler that occasionally clones something; pointed at the right permanent, it turns each attack into a repeatable enters-the-battlefield engine that happens to swing.