Before we are getting chapter 5, is everyone on the same page that Ramb, is in fact a shadow boss.

Ramb is controlling the shadow mantle right?

The OST is named Eram, electronic Ramb.

He "dies" and does not return to Castle Town with us.

He gives us an item, instead of turning into it. (Gersom broke the rule too and ch 3 was the first chapter to break from the chapter 1 and 2 formula)

He indirectly gives 99% of player the opportunity to pick up the shadow crystal.

He longs for his old connection with Kris, so he sets up the old game, and turns into the boss for one last, bit of fun.

No one will shed a tear for him because the soul doesn't know him, Kris likely moved on or can only express so little when being controlled by the soul.

His obvious term dropping akin to other bosses.

I don't think it's bait.