Zaros is an almost completely forgotten and unknown god from days of Gielinor's distant past. The player discovers clues about the existence of Zaros during the Digsite quest after finding his Talisman and giving it to the Archaeological expert. The talisman has a text embossed in it that says "Zaros will return and wreak his vengeance upon Zamorak the pretender". The dungeon found during the quest is an ancient Zarosian temple.
Full Digsite quest dialogue
When the talisman is used on the Archaeological expert he will say:
"This object doesn't appear right... Hmmmm..... I wonder...Let me check my guide... Could it be ? surely not... From the markings on it it seems to be a ceremonial ornament to a god named... Zaros? I have never heard of him before. This is a great discovery, we know very little of the pagan gods that people worshipped in the olden days. There is some strange writing embossed upon it - it says 'Zaros will return and wreak his vengeance upon Zamorak the pretender' - I wonder what it means by that? Some silly superstition probably. Still, I wonder what this is doing around here... I'll tell you what, as you have found this I will allow you to use the private dig shaft. You obviously have a keen eye... Take this letter and give it to one of the workmen. And they will allow you to use it"