Sandun was a Time Lord technician who piloted the TARDIS that Straxus was using to find the Eighth Doctor. After many attempts to find the Doctor, there was a power failure. He was solely concerned with keeping the Dimensional stabiliser working. After this failure, they managed to find the Doctor. (AUDIO: Tangled Web)
He sacrificed himself to make sure that the Doctor did Straxus' bidding, and show him that his TARDIS was time rammed. He was in his first incarnation when he died, but the effects of the retro-genitor particles on Srangor meant that he could not regenerate.