If you recall, Terra ended up as the Lingering Sentiment after being trapped in his own suit of armor at the Keyblade graveyard. Using this armor, he beats down Xehanort, then just.... stops. Alright, what is the reason for this? He said in his own words that he'd "set things right" but as far as any of us know, he's been in the keyblade graveyard doing nothing for eleven years. It's not like he's missing his keyblade glider, and he certainly had reason to leave the graveyard, so why doesn't he?