Possibility Tree

The Possibility Tree, (AUDIO: Auld Mortality) also known as the Tree of Infinity, (PROSE: Cat's Cradle: Time's Crucible) was an infinitely large tree composed of the infinite possibilities which branched from every moment, (AUDIO: Auld Mortality, PROSE: The Hunting of the Slook) such that it was the omniverse. It was also a form of Time. (PROSE: The Hunting of the Slook)

The Tree was connected to the Doctor's rose garden, where the flowers "smelt of memories", which itself was a creation of the Doctor's imagination inside the Possibility Generator. From the garden, one could look down on the entirety of the tree, which according to the Doctor one could see unlimited worlds spiralling off from branches. Amongst the locations the Doctor showed Susan) in the tree were the fires of the Aurora Temporalis ("the anvils of Heaven from which all time springs"); the Frost Fairs of Ice-Askar the Winter Star, from which you "skate through the sky and carve sculptures in the clouds"; and the glittering torchlight on the canals of Venice. One could see in the tree "cities and jungles, alien kings and alien creatures. Always darkness, and light, in perpetual battle."

As well as this, the Doctor also could see alternate Gallifreys: one in which they were as steeped in blood as they were currently steeped in dust; one where the the world was dead and all the children died; and one where Gallifrey was ruled by sorcery, not science.

He also, sometimes, thought he could see himself, travelling from world to world in an old TARDIS, just like he always wanted too.

The Doctor said you could become blinded by the sheer scale of the diverse worlds. He was content to stay in the Possibility Tree forever and never go outside, but Susan convinced him otherwise and carefully brought him down through the branches and twigs to reality. (AUDIO: Auld Mortality)