At the beginning of your first main phase, add for each charge counter on Altar of Shadows. , : Destroy target creature. Then put a charge counter on Altar of Shadows.
Legalities
Not Legal
Alchemy
Brawl
Explorer
Future
Gladiator
Historic
Oldschool
Pauper
Paupercommander
Pioneer
Premodern
Standard
Standardbrawl
Timeless
Legal
Commander
Duel
Legacy
Modern
Oathbreaker
Penny
Predh
Vintage
Rulings
2004-12-01
You put the counter on Altar of Shadows even if the creature regenerates.