State-Based Actions & the Rest of the Keywords

State-based actions (SBAs) are automatic checks the game makes whenever a player would receive priority. They don't use the stack and can't be responded to. The most common ones:

• A player with 0 or less life loses the game.
• A player who tried to draw from an empty library loses the game (checked the next time SBAs are performed).
• A creature with toughness 0 or less is put into its owner's graveyard.
• A creature with lethal damage (damage ≥ toughness, or any damage from a deathtouch source) is destroyed.
• A player with 10 or more poison counters loses.
• The "legend rule": if you control two legendary permanents with the same name, you keep one and put the rest in the graveyard.
• A token or copy in a zone other than the battlefield ceases to exist; +1/+1 and −1/−1 counters on the same permanent cancel out in pairs.

Precision matters here. Destroy moves a permanent to the graveyard (and can be stopped by indestructible). Dies simply means "a creature is put into a graveyard from the battlefield" — regardless of how. Sacrifice also moves a permanent to the graveyard but is not "destroy," so indestructible does not save a sacrificed permanent.

• Haste — ignore summoning sickness.
• Indestructible — can't be destroyed by lethal damage or "destroy" effects (but can still be exiled, sacrificed, or die to 0 toughness).
• Hexproof — can't be the target of spells or abilities opponents control.
• Shroud — can't be the target of any spells or abilities (yours included).
• Ward — a cost an opponent must pay when targeting it, or their spell/ability is countered.
• Defender — can't attack.
• Flash — may be cast any time you could cast an instant.