Misunderstood Trapeze Elf

{TK}{TK} — Whenever you cast a spell, this creature gets +X/+X until end of turn, where X is the amount of generic mana in that spell's mana cost.
{TK}{TK}{TK} — Hexproof
{TK}{TK} — 4/2
{TK}{TK}{TK}{TK} — 6/6