Closing Portals

[Chester]

How would players go about either closing, sealing, or destroying a portal to the Far Realm?

Is there an actual rule somewhere about such methods?

[ksbsnowowl]

Two spells come to mind:
Seal Portal (SpC, Manual of the Planes, and Planar HB)
Gate Seal (FRCS - basically the same thing as Seal Portal)

[Slipperychicken]

You could try burying it, immersing it in magma, or setting up some sort of barrier on one side, like a set of Prismatic Walls or spheres. This way, creatures cannot pass through because there is no space on the other side, or else they are immediately destroyed upon entry. This does not close the portal, but it sure helps keep things under control while you figure out how to do it.

You could set up a second portal right where creatures from the first would emerge. The second portal leads back into the Far Realm (or else to some location which you despise enough to unleash the Far Realm upon), so creatures trying to pass through would simply wind up back in their native plane.

If the portal is generated and sustained by an item (such as a pair of pillars which form an arch which contains the portal), destroying it would be one way to go.

If the portal is simply a permanent magical effect (rather than some technobabble about planar breaches), then dispelling it would be another strategy.

[Kelb_Panthera]

Depends on the type of portal.

A manufactured portal you just break.

A gate spell effect can simply be dispelled.

A natural portal, however, is a bit more difficult. That takes specialized spells like the above mentioned seal portal and gate seal. Simply placing a permanent wall of force across the face of it and building a dungeon around it would give you the classic "sealed evil" vibe. There's just not a lot you can do about these.