You can't lose the game.
Whenever you gain life, draw that many cards.
Whenever you lose life, for each 1 life you lost, exile a permanent you control or a card from your hand or graveyard.
When Lich's Mastery leaves the battlefield, you lose the game.
You donâ€™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.
While you control Lichâ€™s Mastery, your life total still changes. Lichâ€™s Masteryâ€™s effects donâ€™t replace the life gain or life loss.
While you canâ€™t lose the game, your opponents can still win the game if an effect says so.
If youâ€™re dealt more damage than you have cards to exile, youâ€™ll just exile everything you can.
If you run out of other permanents, cards in hand, and cards in graveyard, youâ€™ll have to exile Lichâ€™s Mastery itself and lose the game.