Sustaining Spirit

Cumulative upkeep {1}{W} (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.) Damage that would reduce your life total to less than 1 reduces it to 1 instead.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6oiceed7wvpb1hvi2g4rxi.