Storm decks tend to use black mana a lot, so its especially good there
Token Creature Nightmare Common Raymond Swanland 1/1 NOT LEGAL Standard NOT LEGAL Future NOT LEGAL Historic NOT LEGAL Timeless NOT LEGAL Gladiator NOT LEGAL Pioneer NOT LEGAL Explorer NOT LEGAL Modern NOT LEGAL Legacy NOT LEGAL Pauper NOT LEGAL Vintage NOT LEGAL Penny NOT LEGAL Commander NOT LEGAL Oathbreaker NOT LEGAL Standardbrawl NOT LEGAL Brawl NOT LEGAL Alchemy NOT LEGAL Pauper Commander NOT LEGAL Duel NOT LEGAL Oldschool NOT LEGAL Premodern NOT LEGAL Predh At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature.
Compared to most other attempts at free designs in Magic history, the X-cost caveat is an absolute masterstroke, adding an important wrinkle for deck builders which still leads to usefulness both in fair decks and less fair ones
Only cards that can be played at sorcery speed have the suspend keyword, which means you can only suspend at sorcery speed
Unlike Creature counters, Experience Counters stay with you for the entire game outside of the few niche ways to remove them, like with Final Act