Complex sentence: He tells them that Jacob Carter/Selmak was captured by Sokar and sent to "hell"--actually Ne'tu, the moon of Sokar's homeworld Delmak and that the only person who ever fled from Ne'tu was Jolinar.
Split into simpler sentences: He tells them that Jacob Carter/Selmak was captured by Sokar and sent to hell. He also says that this hell is the moon Ne'tu, which is the moon of Sokar's homeworld Delmak and that the only person who ever fled from Ne'tu was Jolinar.