Things You'll Need
Instructions
Load your character in the game and proceed to Vermilion City. Head to the dock and speak to the sailor at the Ferry Access.
Proceed to Birth Island via the ferry. When you arrive, you will land on an island with a black triangle in the middle.
Go to the bottom of the black triangle and touch it. Afterwards, step down and go left, then go three steps to the right and head up. Head five steps down, then proceed to the extreme right.
Proceed three steps up, then go left, then go to the far right, two steps left, and head all the way down. Afterwards, go one step down and proceed to the left. Head to the far right again, three steps left, then down. You will complete the black triangle puzzle.
Save your game and examine the black triangle to reveal Deoxys. Engage Deoxys with a psychic resistant Pokemon.
Attack Deoxys to reduce its hit points. Use weakening abilities like static, synchronize, or effect spore to induce sleep or paralysis. Use "PP" restoring items during the fight when Deoxys uses pressure so you can continue using abilities.
Throw Ultra Balls at Deoxys when its hit points are very low. If he escapes from the Ultra Ball, continue throwing more of them each round until he is captured.