Alchenolik, Astartes Librarian

Vigilante, Lifelink, Hexproof.

{t}: Add {b} or {u} to your mana pool.

{2}{t}: You get {e}{e} (two energy counters)

Whenever Alchenolik, Astartes Librarian attacks,
you may cast a spell with mana value X or less from your hand without paying its mana cost, where X is the number of attacking creatures.