He raised his hands in the classic pose he’d learned years before, and rasped, “Stand back! Or I’ll fill you full of magic!”
“The magic has faded,” said the man. “The star has taken it away. All the false wizards said their funny words and then nothing happened and they looked at their hands in horror and very few of them, in fact, had the sense to run away.”
“I mean it!” said Rincewind.
He’s going to kill me, he thought. That’s it. I can’t even bluff any more. No good at magic, no good at bluffing, I’m just a –
The Spell stirred in his mind. He felt it trickle into his brain like iced water and brace itself. A cold tingle coursed down his arm.
His arm raised of its own volition, and he felt his own mouth opening and shutting and his own tongue moving as a voice that wasn’t his, a voice that sounded old and dry, said syllables that puffed into the air like steam clouds.
Octarine fire flashed from under his fingernails. It wrapped itself around the horrified man until he was lost in a cold, spitting cloud that rose above the street, hung there for a moment, and then exploded into nothingness.
There wasn’t even a wisp of greasy smoke.
Rincewind stared at his hand in horror.
Twoflower and Bethan each grabbed him by an arm and hustled him through the shocked crowd until they reached the open street. There was a painful moment as they each chose to run down a different alley, but they hurried on with Rincewind’s feet barely touching the cobbles.
“Magic,” he mumbled excitedly, drunk with power. “I did magic…”
“That’s right,” said Twoflower soothingly.
“Would you like me to do a spell?” said Rincewind. He pointed a finger at a passing dog and said “Wheeee!” It gave him a hurt look.
“Making your feet run a lot faster’d be favorite,” said Bethan grimly.
“Sure!” slurred Rincewind. “Feet! Run faster! Hey, look, they’re doing it!”
“They’ve got more sense than you,” said Bethan. “Which way now?”
Twoflower peered at the maze of alleyways around them. There was a lot of shouting going on, some way off.
Rincewind lurched out of their grasp and tottered uncertainly down the nearest alley.
“I can do it!” he shouted wildly. “Just you all watch out – ”
“He’s in shock,” said Twoflower.
“He’s never done a spell before.”
After threatening to turn them into rosebushes, getting dragged by his friends into the magic shop and passing out:
Rincewind opened his eyes and lay for a moment looking up at the stuffed reptile. It was not the best thing to see when awakening from troubled dreams…
Magic! So that’s what it felt like! No wonder wizards didn’t have much truck with sex!
Rincewind knew what orgasms were, of course, he’d had a few in his time, sometimes even in company, but nothing in his experience even approximated to that tight, hot moment when every nerve in his body streamed with blue-white fire and raw magic had blazed forth from his fingers. It filled you and lifted you and you surfed down the rising, curling wave of elemental force. No wonder wizards fought for power…
The Light Fantastic by Terry Pratchett, pages 165-167, 182-183