You may be looking for Jasko or another Sontaran named Jask.

Jask, also known as Jask the Foe Slayer, was a Sontaran commander and a member of the Ninth Sontaran Battle Fleet.

He was sent to Drakkis without armour and guns, which the Eighth Doctor found unusual. He was testing a Sontaran technology after being sentenced to Sontaran Ordeal, a punishment for dishonour conduct. He explained to Sarana Teel about the Time Lords acts in the Last Great Time War that changed the timeline on Drakkis. Because of the teleportation experiments he was dying. He managed to get the Sontarans to hear of Stenk's treachery and get him court martialled before he died. (AUDIO: The Sontaran Ordeal)

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