Magmatic Core

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.) At the beginning of your end step, this enchantment deals X damage divided as you choose among any number of target creatures, where X is the number

of age counters on it.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6ohmtocogvpb1hqtc8d0y4.