Flare of Fortitude

Official rulings

1. Spells and abilities that would normally cause you to gain or lose life still resolve while your life total can't change, but the life-gain or life-loss part simply has no effect. (2024-06-07)
2. The effect of Flare of Fortitude doesn't prevent damage. Rather, it changes the results of that damage. For example, if a creature with lifelink deals damage to you, you won't lose any life, but its controller will still gain that much life. Similarly, if a creature you control with lifelink deals damage to another player, that player will lose life but you won't gain any life. (2024-06-07)
3. In a Commander game, the damage dealt to you by commanders will still be counted, even if that damage doesn't cause you to lose life. (2024-06-07)
4. If an effect says to set your life total to a certain number, that part of the effect won't do anything. (2024-06-07)
5. Effects that replace an event with having you gain life (like Words of Worship's effect does) or having you lose life will end up replacing the event with nothing. (2024-06-07)
6. Effects that would replace having you gain life with some other event won't be able to be applied because it's impossible for you to gain life. (2024-06-07)
7. If a cost would include causing you to gain life, that cost can't be paid. Similarly, you can't pay a cost that includes the payment of any amount of life other than 0 life. However, you can choose to be dealt damage, even though that damage won't result in your life total changing. (2024-06-07)
8. If an effect would cause you to exchange life totals with another player, the exchange won't happen. Neither player's life total changes. (2024-06-07)
9. Abilities that trigger whenever damage is dealt to you will still trigger because that damage is still dealt, even though your life total doesn't change as a result. (2024-06-07)