NPC Coding: Weapons, Spells, Effects

I am building some NPC with unique effects.
First, one of the NPCs has Wave, an artifact that reduces a character by half HP on a critical hit. Can I code this into an NPC, and how?
Second, I want one of the NPCs to be able to Rage like a PC barbarian. Can I add this effect to an NPC character block?

I have Better Effects Gold as well.

Sorry if this may have been asked before, I cannot find a thread like this.
Thank you

I don’t know a way to reduce hp by half. It can be done but I don’t think anyone has built that.

Npc rage you can just apply the same pc rage effect to the npc.

As said, the reduce HP by half will require an extension. I'm not aware of any that currently do this.

There is a barbarian in the Monster Manual Expanded, but it does not parse correctly into an effect on the Combat Tracker. I don't think there is language that will correctly parse and NPC action to the correct effect. See: 5E Effects for Advanced Automation - Fantasy Grounds Customer Portal - Confluence (atlassian.net) You will find the manual effect for Rage, and note that their is currently no language to parse the effect from a NPC action.