Class: Lead Box

Days that pass in succession, like lead boxes.

NB: this 'class' would probably work better as a curse or a monster. I suspect that it wouldn't be much fun to play. 

You do not have a body, and are in fact barely sentient. You attach yourself to another member of the party and travel with them. You are invisible and intangible, and have no true form. In the Southern Steppe where they originate, Lead Boxes are called Banshees. They are said to drift down to the surface earth from the darkness between the stars.

All effects of the Lead Box are shared between the person they have attached to, and anyone unfortunate enough to form a trusting emotional bond with that person - this is how Lead Boxes reproduce. 

You don't have stats or HP like normal, and can never truly be slain. If your host is killed you drift slowly downwards into the earth. After the aeons grind the planet to nothing you will float through the dark void for another billion billion years, waiting for a new host to make use of. 

A: Doom, Incision
B: Good Humour
C: The Face
D: Fever Dreams

Doom: The person that you are attached to (henceforth your host) becomes wholly convinced of their doom and insignificance. Emotional reactions to this vary, but are usually volatile. Your host crits and is crit on an 18 - 20, and both they and anyone they attack roll on the death and dismemberment table with disadvantage. Your host's melee attacks also gain +[templates] damage, representing a desperate strength born from terror. You can speak to them, and only to them, and they will experience your speech as something akin to an intrusive thought. 

Incision: When you look at someone, you know what will hurt them most. At minimum this require the DM to tell you about any mechanical weaknesses an enemy has on their statblock, but might also give you information about their family, financial dealings, secret lovers, disavowed insecurities, etc. 

Good Humour: You can start laughing at someone. They won't hear this (your host will), but they will now critically fail when they would normally critically succeed. Every time this happens, they take d6 psychic damage. It feels like a rose thorn or a piece of steel wool lodged in the brain. 

The Face: You can reveal a face to someone. This is always the same face: horrible, smiling-but-hostile, eyes of a predator. It needs a normal face to manifest, but this can be on anyone. Basically anyone who has LOS to a human face can be targeted by this ability - the horror-face will flash over its otherwise-normal features for a split second. Once seen, the face can never be forgotten. You can't use this ability again until your host kills someone, or rolls a critical failure. 

The face:

• Immediately breaks all bonds of trust, affection, or love between the viewer and the person it has manifested on. This can turn lovers against one another, sworn protectors against their wards, parents against their children, etc. 
• Causes an overwhelming disgust response in the one who sees it - this will usually be a violent response if they are used to solving their problems with violence. 
• In combat, causes the person who sees it to check morale or flee. 

Fever Dreams: You can laugh at everyone in a combat simultaneously, but if you do this you also laugh at your host and their allies. While you laugh this way, you can pick things up around your host as though you had four invisible arms - if these are weapons, you can make attacks with them (you have no to-hit bonus). Those that die while you laugh at them disappear, and each of these deaths provides your host with +5 temporary HP, which lasts until the end of the combat.