The Game of Rassilon Wiki

Reyla's TARDIS was the name given to a mythical TARDIS believed lost to time.

Reyla's TARDIS was referred to in a Gallifreyan nursery rhyme:

Reyla and his TARDIS too,
Reyla took her somewhere new.
Reyla broke his TARDIS' heart
And pulled his very world apart.

According to Arch-Cardinal Kalen, the Time Lord High Council had known for some time that the TARDIS was in fact real, and believed it to be the location of an incredibly dangerous weapon known as the Reaper Cortex. After capturing the Doctor, Travis and Millie on Colony 47, Kalen tasked the Doctor with traveling to Reyla's TARDIS, which was trapped inside of the time vortex itself, to retrieve the Cortex. To reinforce their threat, they revealed they had dropped Millie back to her proper place in time, bringing forward the date of her mysterious disappearance from 1987 to 1982. The Doctor instead escaped Gallifrey, but opted to go to Reyla's TARDIS anyway.

Reyla's TARDIS was in fact revealed to be Roman's TARDIS, with an elderly Roman found in the console room trying to hold his ship together. It was also revealed that the Time Lords had also sent a rogue Time Agent, Captain Greg Kinnear, to retrieve the Reaper Cortex. The Cortex was revealed to be a fiction concocted by Roman to distract the Time Lords during their pursuit of the Doctor. (Active Decay)