They can still activate their permanents abilities during your combat, but theyre still restricted on what they can do
Ademi of the Silkchutes Akroma, Vision of Ixidor Angelic Overseer Animus of Predation Basri, Tomorrow's Champion Blacksmith's Skill Bleeding Effect Bonds of Mortality Bulwark Ox Celestial Armor Collective Resistance Dawn's Truce Defend the Rider Earthshape Eater of Virtue Everybody Lives
Its a great surprise use of an expendable creature you plan on getting back anyway
Can You Pay Life if Your Life Total Can't Change
Pair this with the fact that it's also excellent in EDH, and, as I said, you've got all the playability in the world
Underrealm Lich Self-mill is generally the first step in your gameplan, so its very impressive that a five-drop made it this high on the list