Aqua (HFAOW)

Aqua is a canon character debuting as a playable character in ''Kingdom Hearts: Birth By Sleep. ''In regular canon, after fighting Vanitas and the Vanitas-possessed Ventus alongside Mickey, she fights the Xehanort-possessed Terra at Radiant Garden before falling into the Realm of Darkness, where she is to this day.

Heroes From An Old World
Aqua appears in HFAOW after Vanitas explains to Scott what his plan for the X-Blade entails. Aqua heals Scott and fights Vanitas alongside him, until Vanitas summons six Darkside Heartless to do her in. However, similar to her ending in Kingdom Hearts: Birth By Sleep, Terra's and Ventus's Keyblades shine through the Realm of Darkness and kill the six Darksides, also knocking Vanitas to the ground. After Scott shattered Vanitas's helmet, he flees before he can be identified. Aqua talks to Scott about Vanitas's revival, and also tells him a bit about her own past before the God of Dreams (who appeared as a voice) gives Scott the Tornadosword, as well as transportation back to Aleannas. Aqua and Scott are let out above the icy underground cavern, where Aqua knocks Vanitas to the ground like he did to he before Vanitas fought Ventus in their penultimate battle at the Keyblade Graveyard.

Aqua then witnesses Vanitas fleeing, and he sends 1,000 Unversed after them. After a long fight, Nebula goes into her deadly Super Form and kills the remaining Unversed, but at the cost of her health and immune system. Aqua goes with Warp, Scott, E-1,000 Theta, and soon Aero back to the farmhouse, where Candace, Scizzy, Samantha, Wings, Dark, Remy, Heather, Grace, and Hyper Metal Sonic were waiting.

Once there, Scott and Candace get into a violent fight that attracts five Flood Unversed, and after a rather comical fight, she kills all five of them. She overhears Vanitas's dark words to Warp before Warp left his friends because of them, and she then heals Nebula with Curaga magic while also giving Theta the idea to give Nebula some medical armor (she got the idea from her lost battle armor in Kingdom Hearts: Birth By Sleep.)