Tenth Sontaran Battle Fleet

The Tenth Sontaran Battle Brigade was a Sontaran military unit led by Group Marshal Nathan. Turner was also a member.

History
Nathan and Turner managed to get inside the Doctor's TARDIS with a vitrox bomb, plotting to destroy the timeship after they tapped into the power cable to detonate the bomb. After the Sixth Doctor accidentally transported Tegan into the TARDIS, they set about isolating all the TARDIS's power to the control room to lure the Sontarans to them. Tegan accidentally transported Gareth Jenkins to the TARDIS, and the Doctor got Gareth to help lay a trap for the Sontarans.

When the duo of Sontarans arrived in the control room, Nathan immediately recognised Gareth as the Earth Defence Force leader who would defeat them in the future, in 2001. They were killed by Gareth when he activated the trap which shot pressured steam at the Sontarans, brutally killing them. Outside, the rest of the fleet surrounded the TARDIS in space. (HOMEVID: A Fix with Sontarans)

Later, when Tegan remembered the adventure whilst in conversation with the Sixth Doctor, she imagined that she was in a film, perhaps there would be a black and white flashback to the Sontaran duo, with low-angle shots lit by moody lighting. (PROSE: Fixing a Hole)

Notably, the Tenth Sontaran Battle Fleet later invaded Earth in 2009. (TV: The Sontaran Stratagem, et al.)