Articuno will disappear once you defeat it in HeartGold however you can bring it back in its place within Seafoam Island by defeating the Elite 4 and Lance regardless of whether you've already defeated them or not. Defeating Lance will activate the regeneration process for any Pokémon such as Articuno that is either considered a Legendary or a one-off Pokémon such as Sudowoodo.
Chat with our AI personalities
It is gone. If you saved the game after you killed it then it is gone forever.
Well, you better not have saved the game after articuno fainted because if you did it is gone forever! Other wise simply resart and find your way back again! **Tip** When you find a legendary save the game right in front of him so if you do kill him you can switch off and back on your game and you will have another go! and if you did save the game after killing it, if you have Pokemon XD gale of darkness then you can trade Articuno from that. and any of the other legendary birds. +lugia for the pokedex.
You can't die, if you mean what happens if all your Pokemon are fainted, you just go back to the last Pokemon center you've visited.
nothng happens
nothing.