You could trade for it from someone else, otherwise finding it in the wild, cheats would be required.
Darkrai.
A Mystery Gift event will be starting on May 9th for Darkrai.
Darkrai can only be obtained via trading with someone who has it. The event for Darkrai was only for DPPt.
You can only find Darkrai through a Pokemon Event.
you find darkrai on the bridge on mount kosicotsku
Darkrai can be found at Newmoon Island, but you can't do it without cheats. If you use the walk through everything cheat and you are at Full Moon Island, where you can find Cresselia, you have to walk to the right until you get at Newmoon Island. There you can interact with Darkrai.
Darkrai is a Pokemon from Generation IV, and Pokemon ruby is a game from Generation III , so you can only get darkrai in Pokemon Platinum, Diamond or Pearl
find out for yourself you lazy cheats
You cannot find the Pokemon Darkrai in Turnback Cave in the game Pokemon Diamond. Instead you can find him in Newmoon Island.
you can go to a cave and use your drowsing machine to find it
U find Darkrai in Dark Crater.