The Vault of Lights is a section of the Exodar that has a number of trainers, and is the favorite haunt of the Prophet Velen. A holographic museum of several Burning Legion minions takes up most of the Vault, presumedly for the training of the next generation. Tour groups regularly view the displays.
This area houses the Vindicator's Sanctum (paladin trainers), the Hall of Mystics (mage/portal trainers and wand/reagent vendors), and the Anchorites' Sanctum (priest trainers). At the top of the stairs, on the platform, are the Battlemasters and the Prophet Velen.
The Vault is notable for its central area, which looks like a set of purple holograms of various mobs. It is in fact a museum or tactical information data bank of several Burning Legion units. Of interest is the draenei NPC tour group that strides from one hologram to another. As these NPCs approach various hologram emitters, the emitters state facts about the particular unit, namely the name, the species, its affiliation, and its function. A small enclosure in the corner houses Herbalism/Alchemy trainers, and a spiral transparent walkway leads up to a second entrance for the Exodar, overlooking Valaar's Berth.