Three-headed Goblin god of death. He is often seen with a pig head, a Human head, and a Troll head. - Arcazion Pit (GS-ADV7)

A sacrifice of sorts is typically required to gain his favor.

“The moment you gaze upon him, he requires a sacrifice. If he approves your offering, he will grant you a favor: either to kill one of your enemies or spare the life of a friend.” - Gundur

Death-worshippers of Shintal may bear the mark of their god;

A surprising number of them have the same tattoo, a skull with the number “3” inscribed over its forehead.
…
“That’s the symbol for Shintal, the three-headed Goblin god of death.“ - Pulgor, Festival of Heroes (GS-ADV1)

A surprising number of the patients have the same tattoo on their left shoulder: a skull with the numeral “3” written on it. - Festival of Heroes (GS-ADV1)

At the time of Queen Gimnax's rule, cult worship of Shintal was forbidden;

You interview a few of the death-worshippers, but they’re understandably tight-lipped when it comes to discussing the cult. Queen Gimnax recently outlawed the worship of Shintal. - Festival of Heroes (GS-ADV1)

While exploring the Temple of Ulos, you find Castien kneeling at the statue of Shintal.

“I have prayed,” he explains, “and received a vision. I was not meant to die. The gods sent you to intervene on my behalf.” - Castien - Servants of Azema (GS-ADV2)

You meet Shintal at the Scrying Pool, near the edge of the Arcazion Pit. The god of death is very interested in the upcoming battle.

Shintal smiles at you from the scrying pool. “Sacrifice as you will,” he says. “And return if you find yourself in need. I will be watching this battle with interest.” - Arcazion Pit (GS-ADV7)