It had been an effort to find so many magical artifacts. The Alicorn Amulet, enchanted horseshoes, Starswirl's lost tome of forbidden magic, and more. The magic of the Alicorn Princesses churned within the amulet, granting it their powers and neutralizing its own, allowing Twilight to stave off the madness. All the magical artifacts she carried assured Tirek could not simply draw her magic and end the fight.
She threw up defensive spells and wards to protect herself as she watched him draw in power. Her magic was trained, skillful, manipulating the energy with precision and purpose, while his was brutal, raw, and chaotic. She knew she could not best him in a match of pure physical strength - all she had to do was weaken him, dispel the various magics that currently coursed through him, and when he got weak enough, she could use Starswirl's Banishment spell to send him back to Tartarus - if he was weak enough, the spell could squeeze every last bit of stolen magic out of him, but if he wasn't it would not work, and she would be too weak to try again.
While I delay the end of the MLP Project to torture you poor fools, I had a bit of an artistic burst of inspiration that drove me to draw. You know, for funsies.
So what do we have here?
Well, remember that Alternate Universe idea I had where, instead of becoming a princess, Twilight becomes a wizard? Well, this is the fight with Tirek in that concept. I was going for a "Brains vs Brawn" concept - instead of Dragonball Z energy blasts, Twilight would weave intricate spellwork while Tirek used the more savage and brutal tactics seen in the actual show.
I don't know, this is what happens when you think too much. LOL.
MLP:FiM (C) Hasbro/Lauren Faust