At the beginning of your upkeep, if your opponents control no permanents with bounty counters on them, put a bounty counter on target creature or planeswalker an opponent controls.
Whenever a permanent an opponent controls with a bounty counter on it dies, you gain 3 life and draw a card.
Chevill turns your removal and your opponents' creature deaths into a steady stream of cards and life. Each upkeep you mark a target with a bounty, then you kill it (or let combat/blockers do the work) to gain 3 life and draw, snowballing card advantage in a grindy BG midrange shell. You win by out-valuing the table and converting your advantage into a big board or a combo finish.
Repeatable card draw and lifegain attached to a cheap, recastable commander
Deathtouch makes Chevill a strong blocker and great with ping/fight effects
Thrives in a removal-heavy meta where creatures die constantly
BG offers deep ramp, recursion, and the best removal suite in the format
Bounty trigger is opponent-dependent and easy to play around if they don't commit creatures
Slow without proactive removal to actually kill the bountied permanent
No built-in evasion or finisher; can durdle into card advantage with no payoff
Vulnerable to going wide token strategies and fast combo decks
Card-draw engine that pairs with Chevill's value-grinding gameplan.
Lean into cheap, repeatable removal (Bedevil, Snuff Out, edict effects) so you always have a bountied target to kill on your terms. Add fast mana and tutors (Demonic Tutor, Diabolic Intent) to find an actual win condition rather than just durdling, and consider an aristocrats package (Blood Artist, Viscera Seer, persist creatures) to turn all the death triggers into a closing combo.