Dynavolt Tower is a rare Artifact card from Kaladesh (KLD), collector number 208. Current market price: $0.33 (foil $0.56), TCGplayer market prices via Scryfall.
Whenever you cast an instant or sorcery spell, you get {E}{E} (two energy counters). {T}, Pay {E}{E}{E}{E}{E}: This artifact deals 3 damage to any target.