Lys Alana Scarblade

The genius here is the second cost. The activation is free in mana, so the real price is the discard, and the discard has to be an Elf card: the same resource that powers the kill. That couples two numbers a tribal deck already wants high. The more Elves on the battlefield, the larger the -X/-X swing; the more Elves in hand, the more times you can pull the trigger. A wide Elf board makes each activation lethal to nearly anything, while a thin one makes the ability a chump's wishful thinking. This is removal that scales with the exact thing your deck is doing anyway, which is why it reads as a repeatable sink rather than a one-shot. The discard cost also turns dead Elves (the seventh copy in hand, a creature you would never cast) into removal fuel, so the deck rarely wants for ammunition once it commits to the tribe. The tax is real: you are spending cards to spend cards, and against a deck that can race a 1/1 with a tap ability, that exchange can fall apart. But the trade it offers is the one a flooded Elf deck most wants to make, converting a saturated hand and a crowded board into instant-speed creature destruction. It belongs to the same design idea as other count-the-tribe payoffs, with the wrinkle that it asks you to feed the tribe back into itself rather than simply count it.