Disclaimer: I don't own Buffy or Angel or Wesley.
"Angel, that's half a good plan, and half the stupidest thing anyone's ever thought up. I can get away with betraying you, but to attack an ARCH-MAGE with the piddly small magics at my command? Doomed to failure. But I have another thing in mind. I'll just need to get a couple of items from the vault."
Cyrus Vail looked at Wesley. "So you're here to betray Angel?"
Wesley said, "Yes, and I've got a couple of items that will do the job." He brought out a small sphere with a pin-locked cover over a red button; and an evil-looking dagger.
"Hmmmm, I can see the dagger is necromantic magic. Oh, a soul-drinker?"
"And the other item has some kind of abjuration.....What are you doing?!?"
Wesley had just yanked out the pin and flicked open the cover. He gave a nasty grin as he pressed the button. There was a kind of ripple that bounced off the walls, then back into the sphere.
"It's a new experimental techo-magic device. An anti-magic BOMB. No new magic may be worked in this room for quite a few minutes."
Cyrus Vail was brought up short in his attempt to back away by his oxygen tubing.
Wesley pulled the dagger from it's sheath as he advanced on Vail. "There are two expressions that apply here: One: A slight rephrasing to fit the circumstances: Youth and Treachery will overcome Experience and Power. Two: No matter how subtle and powerful the wizard, a knife between the ribs will seriously cramp his style."
Wesley smiled in unholy glee as the Morganti blade irrevocably destroyed Vail's supposed soul.