Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)
Other creatures you control have dethrone.
Whenever a creature you control with a +1/+1 counter on it dies, return that card to the battlefield under your control at the beginning of the next end step.
Marchesa keeps your board of countered creatures effectively immortal—they die and come right back at end step under your control—while you grind value from ETB/death triggers and aristocrats engines. Early turns deploy counter-enablers and sacrifice outlets, mid-game you loop creatures for advantage, and you close by draining the table or going wide with recurring threats. Dethrone steady-builds your army against whoever's ahead on life.
Persistent, hard-to-remove board through Marchesa's recursion
Excellent synergy with aristocrats, ETB value, and steal effects
Sacrifice outlets convert recursion into repeatable triggers and combos
Grindy attrition resilience that outlasts removal-heavy tables
Recursion only works while Marchesa is on the battlefield—she's a removal magnet
Needs +1/+1 counters AND a sacrifice outlet to fully function, a two-piece setup
Exile, -X/-X, and counter-removal effects shut the engine down
Mana-hungry three-color base with demanding fixing
Doubles +1/+1 counters, supercharging dethrone and your engine creatures.
Tighten the two-card combo lines (Mikaeus + sac outlet + Walking Ballista or Triskelion) and add fast mana like Mana Crypt, Jeweled Lotus, and signets to deploy Marchesa ahead of schedule. Improve interaction with efficient removal and counterspells to protect her, and add a few tutors (Demonic, Diabolic Intent) to find your engine. Trim slow value creatures for instant-win payoffs to raise the ceiling toward high-power.