Damage that would reduce your life total to less than 1 reduces it to 1 instead.
Regler omkring kortet.119 Damage119.1 Objects can deal damage to creatures, planeswalkers, and players. This is generally detrimental to the object or player that receives that damage. An object that deals damage is the source of that damage.119.1a Damage can’t be dealt to an object that’s neither a creature nor a planeswalker.119.2 Any object can deal damage.119.2a Damage may be dealt as a result of combat. Each attacking and blocking creature deals combat damage equal to its power during the combat damage step.119.2b Damage may be dealt as an effect of a spell or ability. The spell or ability will specify which object deals that damage.119.3 Damage may have one or more of the following results, depending on whether the recipient of the damage is a player or permanent, the characteristics of the damage’s source, and the characteristics of the damage’s recipient (if it’s a permanent).119.3a Damage dealt to a player by a source without infect causes that player to lose that much life.119.3b Damage dealt to a player by a source with infect causes that player to get that many poison counters.119.3c Damage dealt to a planeswalker causes that many loyalty counters to be removed from that planeswalker.119.3d Damage dealt to a creature by a source with wither and/or infect causes that many -1/-1 counters to be put on that creature.119.3e Damage dealt to a creature by a source with neither wither nor infect causes that much damage to be marked on that creature.119.3f Damage dealt by a source with lifelink causes that source’s controller to gain that much life, in addition to the damage’s other results.119.4 Damage is processed in a three-part sequence.119.4a First, damage is dealt, as modified by replacement and prevention effects that interact with damage. (See rule 614, “Replacement Effects,” and rule 615, “Prevention Effects.”) Abilities that trigger when damage is dealt trigger now and wait to be put on the stack.119.4b Next, damage that’s been dealt is processed into its results, as modified by replacement effects that interact with those results (such as life loss or counters).119.4c Finally, the damage event occurs.119.5 Damage dealt to a creature or planeswalker doesn’t destroy it. Likewise, the source of that damage doesn’t destroy it. Rather, state-based actions may destroy a creature or planeswalker, or otherwise put it into its owner’s graveyard, due to the results of the damage dealt to that permanent. See rule 704.119.6 Damage marked on a creature remains until the cleanup step, even if that permanent stops being a creature. If the total damage marked on a creature is greater than or equal to its toughness, that creature has been dealt lethal damage and is destroyed as a state-based action (see rule 704). All damage marked on a permanent is removed when it regenerates (see rule 701.12, “Regenerate”) and during the cleanup step (see rule 514.2).119.7 The source of damage is the object that dealt it. If an effect requires a player to choose a source of damage, he or she may choose a permanent; a spell on the stack (including a permanent spell); any object referred to by an object on the stack, by a prevention or replacement effect that’s waiting to apply, or by a delayed triggered ability that’s waiting to trigger (even if that object is no longer in the zone it used to be in); or, in certain casual variant games, a face-up card in the command zone. A source doesn’t need to be capable of dealing damage to be a legal choice. See rule 609.7, “Sources of Damage.”119.8 If a source would deal 0 damage, it does not deal damage at all. That means abilities that trigger on damage being dealt won’t trigger. It also means that replacement effects that would increase the damage dealt by that source, or would have that source deal that damage to a different object or player, have no event to replace, so they have no effect.