Base Class: Barbarian
The path of insanity does not always mean your character is insane. Insanity only occurs when raged which is set off by extreme fear or anger. Depending on the level different feats are given to the insane which will both harm and help teammates along with yourself. Enemies however will suffer a far more cruel fate unless they are so lucky as to witness a group of men self destruct.
The eyes if madness
Your barbarian laughs maniacally with anger, fear, and excitement written all of their face causing those within eye shot to be afraid(only active in rage). Can only fear enemies once a day with ability and allies within the party will become used to this after x amount of times used as decided by dm. Looking into this characters eyes will cause them to be frightened (char saving roll).
Insightful voices
The voices within your head swirl around you telling you what to do ultimately helping you but leaving your head spinning after the (how ever many dm will allow) times to activate bleed effect. When your head is spinning you have disadvantage on attack rolls for that turn.(wis save but after two turns effect wears off regardless)
Rip and tear
Beginning at 6th level when you have enemies grappled you can feel their flesh within your grasp which excites you causing you to rip and tear with glee.
Unholy screeches
level your barbarian can screech giving them a nasty glow. They now life steal a % of health from enemies they strike.
A thirst for blood
An enemy reaching 5% or less hp can be finished in one hit if within 15 movement of the player even if it is not the players turn but only once per fight (dex or str roll). The player is exhausted for the remainder of the fight and cannot leave a fight forcefully going to the closest creature friend or foe(wis saving throw for attack on next turn if friend).