#marked damage

[magicjudge]

If I have a creature with indestructible that takes what would otherwise be lethal damage, and then later in the same turn loses that ability, does it die?

Yes.

Damage stays marked on creatures until the cleanup step. If a creature loses indestructible while having lethal damage already marked on it, it will die the next time state-based actions are checked.

It won’t die if it previously took damage from a source with deathtouch in the turn, though, as the check for deathtouch damage only applies to the next time state-based actions are checked after the damage is dealt.

[magicjudge]

If I have a 3/3 indestructible creature and i block a 3/3 then the opponent plays a spell that adds a -1/-1 counter to my creature, would the indestructible creature die because it was at 0 toughness?

No.

In the situation you describe, you’ll have a 2/2 creature with indestructible that has 3 damage marked on it. It continues to ignore the damage marked on it just like it did before the counter was placed on it because an indestructible creature can’t be destroyed by marked damage. Your opponent would need to give your creature three -1/-1 counters or otherwise reduce its toughness by 3 through non-damage means.

Remember, normal damage doesn’t reduce a creature’s toughness, no matter what Magic Arena would have you believe. The damage just stays marked on the creature until the turn ends and waits to see if the damage ever equals or exceeds the creature’s toughness.

[magicjudge]

Let's say I have a 5/5 indestructible creature, and I block a 3/3 creature with it. And after blocks my opponent give my 5/5 indestructible -2/-2. Would it survive or would it die?

It will survive.

An indestructible creature can never be destroyed by marked lethal damage. In the situation you describe, you’ll have an indestructible 3/3 creature with 3 damage marked on it. Its toughness would need to be reduced to 0 or less for a toughness-reducing effect to kill it. (Normal damage doesn’t reduce toughness.)

[magicjudge]

Say there is a 6/6 creature equipped with an artifact that gives it +1/+1. I then cast Blastfire Bolt, dealing 5 damage and then destroying the equipment. Does the creature have 2 or 1 life left?

The creature still has 6 toughness but also has 5 damage marked on it. That damage will be removed from it during the cleanup step.

Normal damage doesn’t reduce a creature’s toughness, no matter what Magic Duels would have you believe.

[magicjudge]

If a creature takes damage, turns into a noncreature, then turns back into a creature all in one turn, is the damage still marked on it or does it go away?

Damage stays marked on a permanent until the cleanup step, even if it stops being a creature.