|Level:||Sor/Wiz 6, Warlock 6|
|Components:||V, S, M, F|
|Casting Time:||1 full-round action|
|Target:||The door, chest, or portal touched, up to 30 sq. ft./level in size|
As arcane lock, except much harder to penetrate. Anyone casting knock must succeed on a Will save (using the spell's DC + 5) in order to temporarily suppress the spell's effects; anyone who fails this save takes a cumulative -1 penalty each time they retry within 24 hours. Additionally, it cannot be dispelled by dispel magic, though greater dispel magic does work, and it raises the DC for breaking open a door by 15 instead of 10.
The caster knows when the spell is suppressed (by a casting of knock), as a mental alarm spell. If it is dispelled, they are not alerted in any way.
You cannot freely pass a greater arcane lock as you can an arcane lock; you need to also possess a key, which is the focus you used when you cast the spell. However, this key works only for you. If someone else attempts to use the key to open the lock, they take up to 5d6 electrical damage (as a shocking grasp spell at half your caster level; this part of the spell can be subject to Energy Substitution or similar metamagic feats) and are pushed away from the door (as forceful hand). The key itself is not magical, but even if a locksmith could make an identical key, it would not function. Only the original key will work. If that key is lost or destroyed, there is no way to pass the arcane lock short of breaking it (or the door it's cast on). A Use Magic Device check (DC 30) can fool the spell into thinking the user of the key is the original caster.
Material Component: Gold dust worth 150 gp.
Material Focus: A key made of a precious material, such as gold or silver.