Seal Portal(Planar Handbook)
Level: Sorcerer 6, Wizard 6,
Components: V, S, M,
Casting Time: 1 action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One interplanar gate or portal
Duration: Permanent (D)
Saving Throw: None
Spell Resistance: No
You can permanently seal an interplanar portal or gate.
If cast on a portal, the spell prevents any activation of it, although seal portal may be dispelled by a dispel magic spell.
A knock spell does not function on the sealed portal, but a chime of opening dispels seal portal if seal portal was cast by a spellcaster of lower than 15th level.
In addition, the ability of the gatecrasher prestige class (see Manual of the Planes) to open portals may be able to break through a sealed portal, but if the first attempt fails, the gatecrasher can't try again.
Once the portal is opened, seal portal does not remain in effect and must be cast again.
Material Component: A silver bar worth 50 gp.