Uncle Huai

Long Chen encounters Uncle Huai inside a Fiend Eye on the way to the Nirvana Heaven where he was sealed by the Underworld Emperor's people to guard a Life Crystal that would be used to help the Emperor undergo a nirvanic rebirth. Long Chen at first leads Uncle Huai to believe that he's there to perform an inspection on the crystal but after realizing he's a member of the Undying Race and questioning him a bit LC shows him a few memories of his relationship with Liu Ruyan. Long Chen then offers to free Uncle Huai with the price being to be his body guard until he reaches the World King realm. Uncle Huai is more than happy to accept but doesn't believe it will be that easy, Long Chen uses his Purgatory Eye to absorb the underworld seal which causes them both a huge amount of pain. 
Later on in the Nirvana Heaven Uncle Huai shows his power by easily defeating several Celestial Hierarchs.