The Other Promise is Roxas's battle theme, his usual theme being simply entitled Roxas. It is an orchestral piece that portrays the sombre and troubled life of Roxas, who is Sora's Nobody and therefore non-existent and confused about the truth behind his identity and purpose. A stronger, mellower and deeper version of The Other Promise appears in Drammatica, which features Yoko Shimomura's best work.
The other promise is also the theme heard in all Kingdom Hearts: 358/2 Days trailers seen so far.