Hellcarver rule

[RexFTW]

Whenever Hellcarver Demon deals combat damage to a player, sacrifice all other permanents you control and discard your hand. Exile the top six cards of your library. You may cast any number of nonland cards exiled this way without paying their mana costs.

Do you have to play them immediately or can you play them later? If Hellcarver dies can you still play them?

[heroicraptor]

You either cast them as the ability resolves, or not at all.

[Mark Sun]

Even if Hellcarver Demon leaves the battlefield from lethal damage, the ability will still trigger (assuming it damaged a player). You will still get to cast spells if the ability resolves.