The Whirls.
That was the term that Vel's old master had used to describe the act of losing yourself in the act of manipulating large amounts of magic. Vel had always thought of it as a crude, spiteful way of referring to one of the most dangerous things a mage could do.
"Mages spend their lives training to rule the streams of power around us. But when you lose yourself to the current, when you let your mind float along the stream instead of gripping and controlling it, that's The Whirls."
He couldn't help but hear his master's old voice chiding, cackling in that hoarse, smug tone of his. By the time the focus in her eyes gave way to a dazed look, the horror had dawned on him. Her motions became less precise, more reactionary. Arms whirling with less and less precision with each pulse of magic. The worst part was that by the time she'd set into it, it was already too late.
She slumped against him and Vel stammered wordlessly before he was able to get her name out.
"Twilight? Twilight! That's enough, please!"
She couldn't hear him. He tried to rouse her, to put her hands down and hold her by the wrist to just make her stop, anything to make the flow of magic stop. He saw the last of her violet light go whirling out of her, and he saw her eyes hover between open and closed, and he made a small choked sound. A hand against her wrist, and much of the tension left him.
Okay, she was still alive. This was still a nightmare, but at least--
And then Twilight nearly heaved out of his arms as piercing bolts of renewed power started slamming into the wards. Out of instinct, Vel shielded his crystal against the magical whiplash. He was torn between letting her go and holding onto her even tighter. The terror didn't really set in until she went fully limp but was still shooting veritable torrents of magic into the tower's magical systems.
He stood, made some signs to try and dampen her own magic, but he himself was still drained and all he got for his efforts was sharp backlash and singed forearms. By the time he'd gotten back to his feet, the tower's lights were glowing brightly. Too brightly! The foundations shuddered as dormant systems all came back online at the same time, but that shudder was quickly followed by a sharp jolt as magic bolts started to arc off the runes in the ceiling, jumping around and leaving scorch marks wherever they landed.
This was too much, for both Twilight and the tower itself!
Thinking quick, Vel put himself in the way of the beam, using all four arms to try and capture as much of it as he could into himself. His arm runes sizzled and he could feel that his mana reserves would blow at any moment, but he needed just a couple of seconds to mentally direct one of the tower's windows to open. Using the tips of his fingers to guide the energy, Vel straightened his limbs into a resistance-free path. One pair of hands received all the energy, which flowed through him and out through the tips of his other pair of hands, aimed directly out the window like some kind of exhaust. Immediately, the connection slammed through him and he became a conduit. The damage across his body increased, his chest started to glow orange with all the heat and power flowing through him.
He could only hope that she petered out before he got melted.