trafalgar law one piece card game (047) (OP07-047) 5000 [When Attacking] If your opponent has more DON One Piece - Romance Dawn

In fact, Sheoldred was the first card I thought of when I saw Starscream

You will still lose other types of unspent mana as each step and phase ends

Elrond, Master of Healing FromTheShire: In said scry deck, this does a pretty decent job of slinging counters around and pumping up the team, and then if things are hit with spot removal they at least replace themselves which is useful for creature heavy decks

Liliana is decent at this too but you are not at all short on the three slot

Blistercoil Weird Captive Weird Compleated Conjurer Fluxcharger Frostburn Weird Gelectrode Hydroelectric Specimen Melek, Izzet Paragon Melek, Reforged Researcher Petrahydrox Resonance Technician Spellgorger Weird Spellkeeper Weird Steamcore Scholar Steamcore Weird