Will I lose the game if I dip below 0hp whilst there's a spell that'll heal me on the stack?

Question

Take the following situation

1. I'm at 2 life, I cast Sphinx's Revelation for 2 life gain on the stack.

2. My opponent casts something like Warleader's Helix which deals 4 damage to me

3. I then cast another Sphinx's Revelation for 1 life gain.

Stack wise my life would go like this:

1. Start with 2 life
2. Gain 1 life, for 3 total life
3. Take 4 damage, go to -1 life
4. Gain 2 life, ending in a total of 1 life.

So I end up at 1 life, but at one point, my life total was -1. My question is this: Does the stack continue to be carried out until it's complete, or would the game end the moment my life becomes 0 or less?

Answer 1

If I understand the situation you are describing correctly it is as follows:

• A player at 2 life casts Sphinx's Revelation with X = 2. this is put on the stack.
• His opponent responds by casting Warleader's Helix
• The initial player in turn responds by casting Sphinx's Revelation with X=1
• Both players pass priority until the stack is resolved or some other event occurs

This being the case, the following would happen:

1. Sphinx's revelation with X = 1 resolves, you gain 1 life to be on 3.
2. State based actions are checked (technically, twice immediately in succession as both players pass priority) and everyone is still alive
3. Warleader's helix resolves (because the players have initiated a shortcut of passing priority until the stack resolves), you take 4 damage to be on -1
4. State based actions are checked. You are dead. the game ends.
5. Nothing to see here, the game finished. Sphinx's revelation with x = 2 never happens.

State based actions occur whenever a player would get priority, not just when the stack resolves.

Answer 2

You will lose the game immediately after Warleader's Helix resolves, without getting to heal back into the positives.

This is because of state-based actions are checked every single time someone receives priority¹ (rule 704.3), and you receive priority after each item on the stack resolves² (rule 116.3b). The first state-based action checked is if someone has 0 or less life (704.5a), and if so, they lose the game.

Since you receive priority and check for state-based actions between each and every spell on the stack resolving, you will lose once Warleader's Hex finishes resolving and puts you at -1 life.

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<sub>Addendum: these rules have quirky and useful side-effects.
1. But they are not checked during spell resolution. This means you can have less than 1 life total during the resolution of a spell, so long as it's back up at 1 or more by the time the spell is fished resolving. That won't help you here though.
2. This also means that you can cast instants whilst the stack still has spells resolving. If the stack has A and B on it, then B resolves, you can put C on the stack, and that will resolve too, before A finally does.</sub>