You can obtain Palidor by returning to the Solitary Island at any time after you find the Falcon. Palidor teaches the valuable Haste2 and Slow 2Spells, multi-target versions of the originals that can turn the tide of tough battles.
Sonic Dive causes all targets to immediately make a Jump attack. Because this takes every Character out of combat for a time, you can use it to avoid otherwise unavoidable party attacks.