Sora, Donald and Goofy met him at hollow bastion with his hood which means his identity is secret Xigbar confused sora with willie words leaving sora with no idea if his words are true or false.
During the worlds revisited part of the story in the land of Dragons world you find in out its not riku but Xigbar(unmasked) he then flees the scene with his sniper nobodies left to fight sora. It possible he created the heartless named "Stormrider" but if he did create it, it would only have been used to extract the giant heart it contained since hearts are what the Organiztion is after (Reaveled by Axel)Xigbar's last jest
Xigbar is later appeared in "the world that never was" which is there stronghold in the Hall of empty melodies where they begin the fight he was trickey cause he tries to stay of reach but Xigbar can be hurt by his own bullets he also has the ability to change the floor useing attack known as "Charge shot" that fires arcing bullets that richote around the field then uses his "Ultima shot" attack which is the ability to shoot bullets from all directions even so Sora, Donald and Goofy defeated him and he's finally eliminated.
xigbar will make an appearance in the Kingdom hearts manga series with a few adaptations from the author but his story will be the same