ok, so the caster raises to a height of 200 over 1-2 seconds. (while he is raising he gets 100% evasion). Then once he reaches the height, the glacier comes out of the ground and extends to its full height (I guess you could create it here but make its initial flying height (in the OE) a - then when it is created it changes its flying height to a + number). When this happens all the nearby enemies are knocked back (but a special sort of knockback where they fly into the air as they move back) and are damaged. The glacier explodes (using any special effect you like (including imported)) and is immediately removed, the special effect should cover the removal so it looks good. Then once it explodes the caster returns to the ground over 0.5 seconds. (he looses the evasion just before he starts returning to the ground.
Hope this is enough info