Spectre Effect

The Spectre Effect is a known phenomenon that acausal beings create.

Description
An acausal being only exists within its own present and the temporal and spatial location that it observes itself to be in. This results in a curious phenomenon where an echo is left of the being in the temporal-spatial location it had once visited, but is not currently present in. This echo is known as a Spectre, and repeats the the actions of the acausal entity that once performed them. The spectre itself is intangible and cannot be interacted with using most methods, though in the cases where such interaction was performed, the entities that the echoes belonged to were not affected.

Spectres are the main way most such entities can be tracked, being used as a metaphorical footprint of a being's journey through time and space.