Mystic Remora

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.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

Secret Lair Drop

Dominaria Remastered

The bond between spellcaster and familiar allows the mage to detect even the smallest of magical ripples—and use them to their advantage.

Paying cumulative upkeep is always optional. If it’s not paid, the permanent with cumulative upkeep is sacrificed. Partial payments of the total cumulative upkeep cost can’t be made. For example, if Mystic Remora has three age counters on it when its cumulative upkeep ability triggers, it gets another age counter and then its controller chooses to either pay {4} or sacrifice it.