Breach spells strip an enemy mage of magical defenses. Lesser spell breach strips two spells, greater spell breach strips four spells, and Mordenkainen's disjunction strips six spells. In addition, a breach will lower spell resistance for ten rounds, excluding resistance from diamond soul. The reduced spell resistance is an extraordinary effect, so it cannot be dispelled (but is subject to other means of removal, such as lesser restoration). A breach will not affect friendly targets, after accounting for the PvP setting.

This stripping operates in a different manner than a dispel. The two could even be considered complementary, particularly in the case of Mordenkainen's disjunction (which both breaches and dispels). When a dispel targets a single creature, it attempts to remove all magical effects (not just defenses) from that creature, but there is a chance of failure for each effect. A breach, on the other hand, removes only a preset number of effects and only those from an established list of spells, but it does so with no chance of failure.

As a guideline, the types of magical defenses stripped by a breach include the ability to avoid detection (e.g. sanctuary), immunities to particular types of effects, immunities to a spell or a group of spells, spell resistance, saving throw bonuses, armor class bonuses, concealment, damage reduction, damage resistance, damage immunity, and damage shields. However, not all defenses that provide these benefits are breachable. Specifically, the spells that can be breached and the order in which they are removed (up to the limit of the particular breach being used) are the following.

  1. Greater spell mantle
  2. Premonition
  3. Spell mantle
  4. Shadow shield
  5. Greater stoneskin
  6. Ethereal visage
  7. Globe of invulnerability
  8. Energy buffer
  9. Greater sanctuary
  10. Minor globe of invulnerability
  11. Spell resistance
  12. Stoneskin
  13. Lesser spell mantle
  14. Mestil's acid sheath
  15. Mind blank
  16. Elemental shield
  17. Protection from spells
  18. Protection from elements
  19. Resist elements
  20. Death armor
  21. Ghostly visage
  22. Endure elements
  23. Shadow conjuration (mage armor)
  24. Negative energy protection
  25. Sanctuary
  26. Mage armor
  27. Stone bones
  28. Shield
  29. Shield of faith
  30. Lesser mind blank
  31. Ironguts
  32. Resistance