You need to push the button on the wall there before defeating Keara. That triggers a fire jet from the ceiling to melt the ice; hitting it again turns off the fire.
There is only a chest behind that wall, containing an axe if you mindread the ghost Velanir (stats in the spoiler, from From Lancet's
Dragon Knight Saga FAQ/Guide) and IIRC some random loot
Velanir's Axe
One-handed Axe L28 (6748 gold)
Melee damage: 34 - 78; Magic damage: 10 - 24; Critical Chance: 8%
+45 to Hitpoints
+2 to Bleed skill
1 empty charm slot
2 empty enchantment slots
