Echelon Spires are Xel'Naga psionic communication and research stations.
In this capacity, they constantly relayed data on the growth and development of all experimental species and worlds. After the destruction of the Xel'Naga, these structures have ceased all communications to and from the homeworld until the events at Bhekar Ro. Once the signal was received, virtually all of the remaining Xel'Naga artifacts became "active" (Halo 2: Installation 05).
Currently, all Echelon Spires are neutral as Watch Towers and can be used by all capable races. Due to recent discoveries and the obvious destructive potential of Xel'Naga technology, each major power in the Koprulu Sector seek to lay claim Echelons. Should this happen, the secrets of the Xel'Naga will allow that power to gain dominance over everyone and everything that stands against them. This is mainly done through Emissary platforms built deep within each structure.
- Build Apex Relay