Silver Kelolons aren't dangerous, but they're extremely hard to kill due to their insane evasion, and the fact that they'll almost always use Flee to escape the battle on the first chance that they get. If both Kaim and Seth are lucky enough to land hits on the little guy, and you have Cooke use Casting Support on Jansen so that he can cast Ground fast enough, you may be able to take one down. The experience for beating one is really nice, but it's just not worth it to hunt them down. If you run into one, sure. Try to kill them, go for it. Just don't expect to beat them before they run off.