Feeblemind

Enchantment (Mind-Affecting)
 * Level: Wiz 1, Sorc 1
 * Components: V, S, M
 * Casting Time: 1 standard action
 * Range: Medium
 * Target: One Creature
 * Effect: Intelligence and Charisma to 1
 * Duration: Permanent
 * Saving Throw: Will negates, -4 for Wiz/Sorc
 * Spell Resistance: yes

This spell sets the intelligence and charisma of the victim to 1. It is useful to disable a spellcaster. The override defeats other enchantments (so Fox's Cunning cannot temporalily bring the victim up to 5).

Tips
Enemy necromancers in level 10 missions may cast feeblemind on you. Fortunately, they willtarget it on anyone, not only spellcasters, so some victims (such as barbarians) might be only minorly disabled. Having a 1 intelligence is less disruptive in DDO than in PnP, because only abilities which directly use intelligence or charisma are disabled. You can still communicate with PCs and NPCs, and remember which end of a sword to stick in monsters.

It is, however, a difficult spell to remove. Like Bestow Curse and Cause Blindness, it is permanent and continues past deaths and logouts. Potions of Remove Curse and Lesser Restoration won't help, but there are other ways, which even level 3 characters can access (it doesn't require Heal, as the PnP version does)