Considering that mages run a LOT of high mana spells, this is good. Probably not meta-defining for standard, but I could see a dragon mage deck in wild running this. Could work as a one-off in control mage decks too.
So a pseudo N'Zoth, just that it has a different requirement and a fixed outcome. Interesting - could be valuable as value turn. However, the summons lack taunt and aren't sticky, although at 5 health somewhat durable.