You may be looking for the Vogans from Voga.

The Vogans were a humanoid race with blue skin and bulbous heads. They required Voganite to survive and enslaved other races to mine it for them. With their Voganite supplies low, they sent an automated spacecraft crewed by their robots to Crallica. In a pretence of friendship, they offered to transport the Crallicans off their dying planet to their own world, but were really planning to process them and enslave them.

When the Third Doctor arrived on their world, the Vogans asked him to transport the Crallicans from the ship to the planet's surface in his TARDIS, offering him a substantial reward for doing so. The Doctor pretended to agree, but knew that the Vogans would double-cross him. He secretly reprogrammed their robots to break the Crallicans' conditioning, then had a robot return the Vogans' bomb to their control centre. When the Vogans tried to destroy the Doctor's TARDIS, they destroyed themselves. (COMIC: The Vogan Slaves)

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