When an "Elemental HERO" monster you control is destroyed by battle: Your opponent chooses and reveals 1 random card from your hand, then, if it is an "Elemental HERO" monster, you destroy 1 monster your opponent controls and Special Summon the chosen monster.
This card is buggy and broken.
Necroshade is revealed, opponent target is destroyed, but Necroshade isn't summoned. :(
From wikia I read:
"This card can be used to Summon "Elemental HERO Bladedge", Elemental HERO Necroshade" and "Elemental HERO Neos", which would normally require Tributes."