Complex sentence: He also gained the ability to collect the souls of the recently deceased and deliver them to Oblivion; while doing so, he appears visible only to the soul he is collecting, and possibly also his teammate Mr. Immortal, who could perceive the original Deathurge.
Split into simpler sentences: He also gained the ability to collect the souls of the recently deceased and deliver them to Oblivion. While doing so, he appears visible only to the soul he is collecting, and possibly also his teammate Mr. Immortal, who could perceive the original Deathurge.