Vitiate

A castle wall stands tall and stark on the horizon - strong and impervious to attacks unless given by a specialized trebuchet. How could an army possibly storm its gates? One option would be to send someone in secret to infiltrate the fortress and open its doors from the inside... Or you could just break the wall down. But wait - didn't I say that the wall was impervious to most attacks? Very true, very true. The spell vitiate will take care of that. It can't affect the whole castle, but it can affect just one small part of the wall to make it weak and start the destruction process. Not many consider this spell an important one to learn - what with the more flashy primal spells and things of the sort - but its uses can be many for the one who exploits them correctly.

Effect

Vitiate compromises the integrity of solid objects and makes them softer and easier to bend or break. The object (animate or inanimate) or area of effect under this spell glows with soft, orange light.

Side/Secondary Effects

If the caster loses concentration during the spell, it will fade away (along with the glow). It takes concentration to keep the spell going.
If the caster fails to complete the spell correctly, the orange glow will waver and flicker just slightly. It may weaken the area slightly, but not nearly enough to make a difference.

Related School

Abjuration

Effect Duration

Indefinite, if focusing on spell

Range

Touch

Level

Intermediate

Applied Restriction

The larger the object, the more energy it takes to vitiate. As such, it's common practice to focus this spell on a single point of weakness to make it even more vulnerable to physical attacks. However, since the caster must have contact, it's a relatively useless spell in active combat unless they're able to get close enough to their opponent. Usually, fortify is a more reasonable spell to use in such cases. 
When the spell is cast on a pebble, or something of similar size, it's possible that it will crumble without any extra outside force. If the spell is concentrated on an entire boulder, however, it will only make it a little easier to smash with a hammer or other bludgeoning weapon of the sort.