Created by and for W. D. Gaster, the MTTD(Multi-Timeline Traversing Device) allows it's user to tamper with only their existence of time; allowing them and them only to warp across to any point in the future or past. However, only twice: Once to go to said location, and another to return to the current time.
The MTTD was used by W. D. Gaster in the events of the Vizon Project and the Evolution Project to stop a child who would destroy the Underground and it's world; halting the events of Vedomitale. However, as Gaster took the SOUL, his work on Project Evolution was completed to an extent. As he returned, he used said SOUL and his own, fusing the two together and forcing them into Broken!Science.