Sylok, the Defiled
From Destiny 1 Wiki
Sylok, the Defiled is a Taken Knight that was captured and imprisoned within the Prison of Elders.
Gameplay
Sylok is just like any Taken Knight in that he is armed with a Void Boomer, he can teleport short distances, and he has the ability to send out Solar projectiles that linger on the ground. However, in Challenge of the Elders, Sylok's ability to do so is dramatically increased. He will fire bigger clusters of those projectiles, and when they land on a surface, they will create a burning spot that will cover a much wider area of effect and last a lot longer, so expect to see Solar spots all over the room.