Lakh was a Seer on the planet which coalesced around the P7E. Along with his companion, Ankh, he interrogated the captured Minyan, Herrick, and discovered the nature of the R1C crew's quest. At the Oracle's instruction, he and Lakh tricked Herrick, by giving him bombs disguised as the Minyan race banks for which Herrick's crew had been searching.
In the hierarchy of the "P7E planet", Lakh was a highly-ranked individual, who reported only to the Oracle. Beneath him were the Guards, and beneath the Guards were the "Trogs".
Behind the scenes
The script of Underworld does not explain Ankh and Lakh in any great detail. It can be assumed that they're androids, but it's equally possible they're humanoids with special helmets. In any case, they logically descend from Minyans or Minyan technology.
The script also does not indicate which Seer is which. Ankh and Lakh are thus indistinguishable on screen.