Djeru and Hazoret

The low-hand condition is the design conceit, and it points backward at the hellbent-adjacent tradition that mono-red aggro was built on: Hazoret the Fervent's own attack restriction, the reason those decks kept their curves low and their hands emptying by turn four. This fused legend inherits that discipline and turns it into a switch. Get down to one or fewer cards in hand and the 5/4 gains vigilance and haste, so it swings the turn it lands and still guards on the back swing; hold more than one card and it is a slower, ground-bound body that leans on its attack step to do the work. And that attack step fires no matter how full your hand is, which is the genuinely novel piece: a combat dig six deep for a legendary creature you cast free, that turn only, at whatever speed the swing allows. It is impulse-draw narrowed to one card type and welded to the aggro plan, so the ceiling scales with how many fat legends you can stack behind it. The tension it resolves is that empty-hand aggro usually stalls the moment the fires die down; here the swing itself refuels, pulling a fresh threat off the top exactly as your hand runs thin. The keyword condition wants you empty; the trigger keeps working even when you are not, so the two halves reward the same aggressive line without punishing you for missing the threshold.