Eternal Sanctuary is a legendary major card out of the New mechanic pool. Sanctuary lasts 16 pulses (40 s) at half strength in a 4.9 u circle.

You can take it once · it only turns up when your Ultimate ability can actually use it · it can be offered for 0 of the 34 abilities.

Only one card can reshape that ability this way — this one, or Hallowed Ground and Searing Sanctuary. Take one and the rest are gone for the run.