So is the reason for Tyren getting more unhinged the side effects of the devotion necklace, or was this a downward spiral he would have gone done regardless of the necklace? I remember you talking about how the necklaces have consequences, and I'm curious if this is one of them.

Yeah!

Tyren would have been an already overly-doting and even jealous character on his own without the loyalty necklace, (and had been due to his crush on the Lamb even before recieving it, and what happens when you reject followers in-game) but his spiral into a unhealthy obsession and idolization was aided by the loyalty necklace.

If it was given to perhaps a regular, less devoted follower, the effects maybe wouldn't have had such severity. But Lamb got the materials/necklace from the mystic seller and isn't fully aware of the effects it might have on their followers yet.

So, dog is unhinged a bit on his own, but amplified by the necklace. He's originally friendly, caring and sweet. But you take good traits, too much of a good thing, and they can turn bad