Waterdeep is known for its worship of Oghma and Deneir, gods of knowledge and the spread of knowledge. Each church maintains a library of its own, but the two churches are in close contact because Deneir serves Oghma. The two churches have different reasons for collecting tomes and these reasons are reflected in the types of tomes that one finds at each of the churches. The church of Deneir, following its god’s interests, collects literature and maps primarily, but it also keeps records of ancient languages and artistic renderings. The church of Deneir is full of scribes that transcribe books for the ever-growing collection. The church of Oghma is interested in knowledge in general (nonfiction), and the songs of bards from across the lands. The two churches share their works to promote the universal spread of knowledge.
Besides their own libraries, the two churches cooperate in maintaining a collective secret library that the church of Deneir takes primary responsibility for. This secret library is located deep inside a mountain and is accessible only via a pair of portals. One portal links the library with the temple of Deneir, and the other links it with the temple of Oghma. Each portal is human-sized and activated by a key.
At the temple of Deneir, the portal is located in the basement where some high-ranking priests have rooms to themselves. The portal appears to be a door, but the door is surrounded by a set of large scrolls that contain part of an old liturgy that has not been used by the church in some fifty years. To activate the portal, one must write in the missing parts of the liturgy where they belong and then speak the whole liturgy. The portal does open if only the written part of the key is completed, but without the oral part, the portal malfunctions. The portal never works properly without both keys. The scrolls magically erase the newly written words once the portal closes again.
At the temple of Oghma, the portal is located on the second floor near some scribes’ chambers, and it’s in a locked room. It too is surrounded by scrolls containing partly completed liturgies, but in this case there are three different liturgies intertwined. To activate the portal, one must complete only one of the three liturgies. Completing the others or more than one results in a portal malfunction that sends the traveler to a remote seaside place on the shores of the Shining Sea. The scrolls magically erase the newly written words once the portal closes again.
In the library, the return portals are creature-only, so that books cannot be removed from the library. The library is protected against teleport spells and the like, but planar travel is allowed so that the protector of the library, Colorrn the Thaumaturgist, can summon monsters to aid him in defense when needed. Colorrn is usually prepared with a scroll to seal any portals created by others into the library. The protections are not as absolute as those at Candlekeep because most of the books here are duplicated somewhere else in the Realms that the clerics can access, so if something happens to the library, they can in time replace all the tomes.