I just found this in the SRD - I'll be using a lot of these I think.
Dimensional Lock
Abjuration
Level: Clr 8, Sor/Wiz 8
Components: V, S
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Area: 20-ft.-radius emanation centered on a point in space
Duration: One day/level
Saving Throw: None
Spell Resistance: Yes
You create a shimmering emerald barrier that completely blocks extradimensional travel. Forms of movement barred include astral projection, blink, dimension door, ethereal jaunt, etherealness, gate, maze, plane shift, shadow walk, teleport, and similar spell-like or psionic abilities. Once dimensional lock is in place, extradimensional travel into or out of the area is not possible.
A dimensional lock does not interfere with the movement of creatures already in ethereal or astral form when the spell is cast, nor does it block extradimensional perception or attack forms. Also, the spell does not prevent summoned creatures from disappearing at the end of a summoning spell.
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Graf, here's my notes on the wizard and the portal, though none of this is set in stone yet. For some of this to make sense you need to know the following:
[IMC, the church of Bane is purging the Zhentarim of Cyricists and generally killing Cyricists all up and down the Sword Coast, the North, the Western Heartlands, the Heartlands and the Moonsea. This has been mostly a "quiet" process done through assassination and night-tme street battles. The Banites have gained the services of mysterious assassins and warriors that the Cyricists have take to calling "the Deathless" since none of them have yet fallen in combat. With the help pf the deathless, the Banites have already purged Darkhold successfully.
Also, the Zhentarim have recently become the biggest trade organization in Baldur's Gate but they still have plenty of competition from other groups and independents. The Church of Bane/Xvim has also regained legal status in Baldur's Gate after being on their best behavior for the last few years and assisting with a virulent plauge that hit the city a year ago. End background]
Eighty years ago a wizard named Gulf came to Baldur’s Gate to retire after a long career of adventuring. He quickly grew tired of life in the city and constructed a small walled keep [Dungeon #99 – pg. 50] atop a small plateau one day’s ride to the north of town (but a half-day off any beaten path). The keep was constructed so that it could only be approached from the southwest by foot or horseback, and half of that trip would be spent hacking through dense growth. Anyone wishing to come by another route would have to use magic. Gulf settled down to a life of quiet magical experimentation for the next thirty years and his speciality was inter-planar travel. In his final years, he devised a way to travel to other "possible" worlds using a magcial creation he called "The Door Between" that led to something he termed "The Nexus of Realities."
These "possible" worlds were like Toril, but different in ways that ranged from large to small. Gulf theorized that these worlds were not really in separate places but in separate “times” and represented divergent possibilities of reality that could sometimes merge or split depending on how fate played out in each. Unfortunately, Gulf became lost in his travels between what he called “possibilites” and was never seen again. He recorded his findings about The Door Between and the Nexus of Realities in his library but his hermit-like nature ensured that no one missed him – and no one in Baldur’s Gate even knew the Wizard was gone. Baldurans didn’t even realize it when a stupid green dragon named Zebbakkukakraz took up residence in the courtyard of the Keep.
Zebbakkukakraz, a truly sorry dragon, was content to sleep, eat deer and play with his big “toy” castle and posed no threat to the city and so was never discovered. He devoured the occasional orc band that came along with thoughts of taking the keep, but this just made Zebbakkukakraz feel like a “King.” Due to his large size and small brain, Zebbakkukakraz never got around to exploring very much of the inside of the keep.
Three months ago, a group of Cyric-worshipers looking to establish a safe fortress to hide from Banites, came upon the keep, slew Zebbakkukakraz and took up residence. They soon discovered the Door Between and, like Gulf, became lost within – all but their least member, a man named Chave (Sha-vay). Who somehow emerged from the Door Between. The experience left his already fragile mind shattered - he was now quite insane.
Chave returned to Baldur’s Gate insane (which is okay for a cyricist really) and in a drunken stupor blabbed about the Door Between to a minor informer of of the Banites. The Banites sent a wizard to investigate the keep. The wizard found Gulf's notes, studied them and with the help of divinations from Banite Clerics, used the Door Between and the Nexus of Realities to partially stabilize a path to a single “possibility” - that to an alternate Toril where the forces of Bane have already won out against all others.
Now the Banites in this reality are negotiating with the Banites of the other realty to send an army through The Door Between to conquer THIS world for Bane. So far, the other Banites have sent through a host of Fire Giants to help guard the keep, but negotiations are on-going. The other Banites have been slow to act because Bane has strangley offered no guidance, despite repeated requests for it. To explain all of this would require many more pages of my note so I'll cut it of with the following:
1. the leader of the "other Banites" is the evil-coutnerpart to one of the PC's.
2. the PCs are mostly good but might be willing to aid the Cyricists on a limited basis because they are REALLY guning for the Banites.
use it.
