Whenever a player sacrifices a permanent, put a +1/+1 counter on Carmen and you gain 1 life.
Whenever Carmen attacks, return up to one target permanent card with mana value less than or equal to Carmen's power from your graveyard to the battlefield.
Build a BW aristocrats engine that sacrifices permanents to grow Carmen and gain life, then swing in the air to reanimate ever-larger permanents from your graveyard. As Carmen's power climbs from sacrifice triggers, her attack reanimates bigger threats and value pieces, snowballing the board while you drain opponents.
Triggers off ANY player sacrificing, so it grows even from opponents' sac effects and your own fodder
Built-in reanimation that scales with her power, recurring sac fodder and bombs for free each combat
Steady lifegain cushions you against aggro and pairs with payoffs
Flying makes her a reliable attacker that's hard to chump
Reanimation requires connecting in combat, so removal or blockers shut off the value loop
Commander-dependent: without Carmen on board the engine stalls
Low starting power (3) limits early reanimation targets until counters accumulate
Vulnerable to graveyard hate that empties your reanimation fuel