The Tieflings dont have anything specific to do with Goblins who are just following the Absolute orders of basically attacking everyone in the area.

I think some Goblins or maybe even Minthara mention something short about Tieflings, but it doesnt make sense they would be solely focused only on them.
It maybe that the writers just tried to create an excuse for their "refugees are a problem because Goblins attacks us because of them!!!" but it doesnt actually make any sense in the overall situation. Because obviously Goblins are attacking everyone they can and Absolute would not leave Druids in the Grove, just hugging trees all day.

Apparently the forces of Hell are interested into the whole deal, but other then they are playing with it all and are not direct allies of the Absolute its unclear exactly in what way they are interested.
And Tieflings are not really directly connected to inhabitants of Hells anyway. Just random people turned into devilish lookalikes and poor refugees. If there is anything else there we never got even a hint.