Aplan

Aplans were the native inhabitants of the planet Alfava Metraxis.

Biology
The Aplans were humanoid lifeforms with two heads. The heads apparently had their own separate intelligences and personalities as, for in at least one period, heads of the same body were allowed to marry each other. The church later attempted to ban this practice. (DW: The Time of Angels)

Culture
According to the Eleventh Doctor, the Aplans were a relaxed and cheerful species - a fact he attributed to them having the constant company of a second head. He also described them as prolific builders, and their civilization left notable landmarks on their home planet of Alfava Metraxis. These included the Aplan Mortaria, sometimes known as Mazes of the Dead. These were large subterranean labyrinths with tombs in the walls, adorned with statues of the dead. The Mazes had six levels, representing the ascent of the soul in the Aplan religion. The Aplans were fastidious at recording their social, cultural and political history. (DW: The Time of Angels)

History
In the 47th century, a large population of Weeping Angels came to Alfava Metraxis, quickly causing the collapse of their civilization and killing them all. Having hunted the Aplans to extinction, the Angel colony lacked any further energy source and over the centuries degraded and went into hibernation. (DW: The Time of Angels)