Gate

The casting of a gate spell has two effects. First, it causes an interdimensional connection between the plane of existence the wizard is on and the plane on which dwells a specific being of great power; thus, the being is able to merely step through the gate or portal from its plane to that of the caster. Second, the utterance of the spell attracts the attention of the sought-after dweller on the other plane. When casting the spell, the wizard must name the entity he desires to use the gate and come to the wizard's aid. There is a 100% certainty that something steps through the gate. Unless the DM has some facts prepared regarding the minions serving the being called forth by the gate spell, the being itself comes.

Gates can also be permanent structures that allow passage from one place to another when activated. In this way, they are similar to the doors of Sigil, but differ in two major ways. First, they require more powerful magic to activate. Second, they remain open for some period of time rather than only as long as the key is in contact with it.

Note: Portions of this version of gate originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.