Elizabeth Summers had built her own TARDIS to look like a Gray Flying Saucer.

The Gray Flying Saucer was a Type 14 Exploration TARDIS.

Elizabeth's TARDIS was more outdated than the 12th Doctor's Type 40 Exploration TARDIS and now the Cybermen had control of it.

900 Overlapping Milky Way Galaxies all connected by the Sunnydale Hellmouth's Dimensional Maze Network.

The First Evil's Dimensional Prison was a maze of several Identical Milky Way Galaxies and all of them had Buffy Summers living inside Sunnydale in case the First Evil tried to escape through any of the Hellmouth Openings.

It was an ironically complicated maze created with several Identical Milky Way Galaxies being duplicated by the Pandorica's Big Bang Two going off simultaneously.

Dimensional Mitosis Created Endless Milky Way Galaxies being duplicated with multiple versions of the 10th Doctor roaming around Identical Sunnydale Cities.

Possessing People quickly became pointless if the Time Lord Doctor had enough resources to Outsmart the First Evil repeatedly into a stalemate.

The First Evil needed to manipulate people without them working together to reverse his possession of their friends.

The Simple Solution was to Fool Buffy Summers into thinking she Destroyed Sunnydale and then bring another Sunnydale across the First Evil's Dimensional Maze.

The problem was the Black Guardian pulling the Planet Gallifrey into the First Evil's Damnation.

Elizabeth Summers and her Stupid TARDIS falling into the First Evil's Personal Hell was bad enough without the Time Lords themselves appearing afterwards.

The First Evil had actually panicked when the New Buffy Summers turned out to have enough Time Lord Knowledge to Steal Immortality from Captain Jack Harkness and construct her own Paradox Machine to chase after the Cybermen Commandeered TARDIS without changing her own history.

The First Evil frowned while watching Elizabeth Summers Reshape History to her own advantage.

The Human Buffy Summers died inside Sunnydale and Elizabeth Summers used her identical appearance to take her place.

It was the first time something unexpected happened to the First Evil's Plans and then the whole balance of power between the Powers that be changed with the Cybermen Invasion into Sunnydale making everything worse.

Having the Cybermen running around the Sunnydale Hellmouth made it impossible for the First Evil to possess anyone without the Cybermen getting in the way. The Time Lord Doctor was one thing and the Cybermen Commandeered TARDIS was another.

The First Evil was once again forced to watch and wait for the Time Lord Doctor to play chess with the fate of the Identical Milky Way Galaxies until the time was right to strike back unseen.