Electrodominance deals X damage to any target. You may cast a card with converted mana cost X or less from your hand without paying it's mana cost.
Could this make something like Ancestral Visions playable in Vintage? We already have As Foretold which sees no play, but As Foretold requires tapping out main phase and needs time to ramp and has no ability by itself (albeit, it's reusable). This spell is instant, just a "plus 2" to the cost of any spell you want to cast, and can kill planeswalkers, weenies, or deal the final damage to an opponent at instant speed.
I can see a situation where you EoT this thing and play instants not in your colors...maybe an As Foretold/Electrodominance UR deck with non-UR spells? You can also cast PWs, artifacts, and creatures off this on your main phase, which you can't with AF.
I liked those "Play a spell with CMC X or less for free" spells in the last block (Sram's expertise for example), but you couldn't cast anything costing more than 3 and you couldn't cheat out a costless card for 2 mana like you can with this. RR = Hypergenisis? Mountain, Ruby/SSG = Emrakul?