While the Frost Stone had lost much of its mana, it still had enough for Tycondrius' purposes. He modified his formation, directing the stone's mana flow into its prison, effectively sealing it until its power decayed.
In a few suns, the ice would freeze over the formation lines, making it nigh-impossible to modify further. Outside of special circumstances, it would take years (hopefully epochs) to recover it. Besides discovering its location, it would then take a specialized team of experts with the proper tools to do so.
By that time, it would no longer be Tycon's problem.
Athena's impromptu ice prison was admittedly a half-measure. It would be far better to place a proper seal on it... hiring a Formation Mage to do so. Then he could hire adventurers to seal it at the bottom of a dungeon with an active Core... or to throw it into a fiery volcano that linked to the Plane of Fire. Such plans, however, risked the secret of its location being leaked.
