The snakes emerged from the edge of the glowing runes into the wall and pillars. The runes are still there, and they are slowly regaining their glow. Everything points to visual illusions, that did not react to magic, but to physical damage.
OOC:
@Lemming23 the observation roll is not needed, and in anycase it should have been 2d12, not d10 ;)
The archmage, the headmaster of the academy, stands up on a table and magically amplifies her voice
Attention all students, guests and staff. Please remain calm. The threat has passed and...
Younger male students are standing to laugh as all of a sudden, this female elven mage, stands entirely naked in front of you all.
In a panic, she janks a magic book to her chest, trying to cover her nudity.
No! What? This can be happening! Her voice is still amplified as she runs off out of the dining hall. Once this young elf got her self a tramp-stamp-tattoo of a dear antlerers, and they are on full display as she flees the room and the many eyes on her.

Master Orin
The archive master stands up in her place and tries to calm things down.
WAIT! SOMETHING IS STILL GOING ON. PLEASE RETURN TO YOUR ROOMS AND STAY THERE UNTIL FURTHER NOTICE.
He turns to professor Reed.
Vivianne, please engage the lockdown
Professor Reed quickly leaves the dining hall, and in less than a minute, a giant translucent sphere* engulfs the entire Angelholm Monastery
OOC:
* it looks like a soap bubble, preventing anyone or anything from entering or leaving the monastery or its emidiate airspace.