If nothing else, a card like this is fun. Everybody can watch it slowly tick down, and everybody can plan for it's eventual arrival. The game suddenly gains a whole new element of long-term strategy.

Being a blue mage, you ought to be able to take all this into consideration and outwit your opponent. An enemy player is likely to hold onto a killspell to deal with the Ephemeron when it arrives, so maybe you'll save a counterspell for that killspell, or maybe you'll just let it soak up the hate, or maybe you'll just pretend to be doing one while you actually do the other, the possibilities are endless!

But honestly, isn't blue all about planning for the endgame?