Q: Blackrazor and Tomb of Annihilation

Question:

How would Blackrazor, and namely its soul devouring trait, work in the Tomb of Annihilation with the Soulmonger's soul eating? We just ran White Plume Mountain and I am taking advantage of the option to start Tomb of Annihilation at 9th level which that adventure discusses. One character has Blackrazor (his task is [or was] to destroy it) but that character is the only one who has died and been raised so far and so his hit point max will be dropping but Blackrazor is supposed to increase it when he kills a creature. It seems the spirit of the adventure is that nothing would increase this character's HP max but I see some potential for fun here, and a motivation for this character to kill something each day. Any thoughts? How would you play it?

I'm not seeing where Blackrazor increases the max hit points. It gives the user temporary hit points but I can't see it changing the hit point max.

True. You are absolutely correct. Blackrazor increases temporary hit points. But it can increase them by a very notable amount. I find it interesting how in the game the max HP is going down which will lead to the player wanting to feed the sword even more. But it feeds by devouring souls which would put it in competition some with Soulmonger. I'm not sure if Soulmonger is a greater power and wins out for the soul over the sword. I don't know, when the thought first hit me, it felt like a perfect marriage for a storyline. Originally, the plan was that Blackrazor has to be destroyed. Normally it is too powerful a weapon [and evil if it doesn't care who it feeds on party, or wielder included] but it may work here for story purposes.