What is the last known information rule and how does it apply when a creature dies?

When a permanent leaves the battlefield — for example, when a creature dies (moves to the graveyard) — it no longer exists on the battlefield for the game to examine. The last known information rule (CR 113.7a, 608.2h, and 700.7) allows the game to use the object's last known characteristics while it was on the battlefield to answer questions about it.

This matters most when a triggered ability or spell tries to refer to a creature that just died. If an effect says 'when this creature dies, return it to the battlefield if its power was 3 or less,' the game checks the creature's power as it last existed on the battlefield — not what it looks like in the graveyard. Counters, Auras, and other continuous effects that were on it at that moment are all part of LKI.

Similarly, if a player controls an effect that triggers 'whenever a creature dies, you gain life equal to its toughness,' the game uses the creature's toughness as it last existed on the battlefield (including any +1/+1 counters or pump effects active at the moment of death), even though those may no longer apply once it reaches the graveyard.

Concrete example: You control a 2/2 Bear that gets -4/-4 from a spell, making it a 2/-2. State-based actions put it in the graveyard. A triggered ability that says 'when a creature you control dies, if its toughness was 2 or less, draw a card' would check LKI and see toughness -2, which is indeed 2 or less, so you draw a card.

LKI does not apply in all situations — notably, if an object changes zones and later another effect asks about 'that object,' the game may be unable to track it (CR 400.7), so LKI only bridges the gap at the very moment of the zone change and for effects directly tied to that event.