2018-04-27 : If you run out of other permanents, cards in hand, and cards in graveyard, you’ll have to exile Lich’s Mastery itself and lose the game.

2018-04-27 : If you’re dealt more damage than you have cards to exile, you’ll just exile everything you can.

2018-04-27 : While you can’t lose the game, your opponents can still win the game if an effect says so.

2018-04-27 : While you control Lich’s Mastery, your life total still changes. Lich’s Mastery’s effects don’t replace the life gain or life loss.

2018-04-27 : You don’t have to exile all the cards from one place. For example, if a source deals 5 damage to you, you may exile one permanent, two cards from hand, and two cards from your graveyard.