Tyvar the Bellicose (Showcase) (98) [March of the Machine: The Aftermath] [Showcase]

Whenever one or more Elves you control attack, they gain deathtouch until end of turn. Each creature you control has "Whenever a mana ability of this creature resolves, put a number of +1/+1 counters on it equal to the amount of mana this creature produced. This ability triggers only once each turn."