Just finished a magic-centric game and it was properly epic with the power and buildup (though I used extra shards setting to keep from being frustrated with the lack of mana, and so I could experiment--nice to have that option). The run-up to the cool endgame pic for a magic victory is lacking some information and missing an opportunity to feel more epic/dramatic. Simple pop-up windows with nice prose about what is happening would both inform the player and build the anticipation.
For example, you could get a message when you build the final tower (those all look sweet, by the way), noting that the Spell of Making is now prepped and ready to cast (a simple alternative to having it just slip into a spellbook that's at least 4-5 pages long by then, and this would give the chance to indicate what the casting entails--that you would be staying in one spot and focusing for many seasons, though I suggest that 25 is far too many and gets laborious--how about 12?). Another great chance for flavor text is when you cast the spell, something about a subtle change relating to each of the elements, something to enforce the epicness of what is happening (ex: "Oceans become mirrors of glass, every wave stopping to hold its breath. The wind shifts and swirls, waiting. And with the subtle rumble in the ground, the earth itself takes notice. Even the humblest of cooking fires seems to know a rebirth is beginning. With protective armies arrayed around <leader>, <he/she> draws deeply upon each of these elements.").
Then a final pop-up text could come halfway through (a good addition to the simple progress bar) about the shards resonating, aligning, amplifying. All this would give that final cut scene even more weight/meaning.
Please consider it, because as it stands now, it's like a poor ending chapter of an otherwise engaging novel.