Hello. The lander page for worldofwarcraft.com says the following:
The Shadowlands are open and Season One has begun. Face deadly foes, earn new rewards and achievements, and raid Castle Nathria, Sire Denathrius’ fortress in the dark heart of Revendreth.
I bolded the mistake. Denathrius’ should be Denathrius’s. I know it looks incorrect but it’s the grammatically correct spelling. Denatharius’ would imply there’s multiple Denathrius and the fortress belongs to them. However there’s only one of him, and so Denathrius is a singular proper noun, meaning we add the ‘s. A lot of people assume if the letter S is at the end of a word that you make it S’. A good rule of thumb is that if you have to specifically pronounce it, it’s 'S.
You don’t pronounce ‘The dogs’s toys’ and so likewise you wouldn’t add ‘s to the end of it. In this instance you would pronounce dogs as dogs, and spell it ‘The dogs’ toys’.