Portals & Planes

From the back of the book:

The definitive d20 System resource for plane travel.

This invaluable sourcebook provides DMs and players everything they need to create and run ploanar adventures and campaigns.

• Complete rules and guidelines for creating characters suitable for plane travel and world-hopping, as well as new prestige classes, feats, spells, and magic items.

• Comprehensive descriptions of several different portal types, including their traits, characteristics, and game statistics.

• Rules and guidelines for designing an endless variety of new worlds and planes.

• Guidelines for altering existing creatures to create planar variants, and complete descriptions of many new extraplanar monsters and allies.