To get deoxys you have to have meter cave on your map then you need to wear tight belt before you into the dungeon then you need to have 1 friend bow on your inventory when you get to deoxys you put it on which he is in floor 20th but you need to kill illisons of deoxys on each floor oh and also bring 1 max elixer because pp of each move is double so if you trow 1 ember is like you trow 2 ember. sorry for some spelling mistakes.