Poise

Poise is your ability to take a hit and still stand.

Poise is broken when you take more than half your current HP in damage (before mitigations) in a single round of combat.

So if say for example, you are wearing Grade 4 Heavy armor, you have 12 HP, and an enemy with an SMG shoots you for 6 damage. Even if none of the D6's beat your Grade 4 armor and deal damage to your HP, you still get knocked prone.

If your poise is broken, then you are knocked prone. While prone, you cannot take any additional poise damage and like D&D, ranged attacks are at a disadvantage to hit while prone.

Bludgeoning melee attacks and certain shotgun attacks deal double their damage value to your poise, or alternatively, if they deal a quarter of your current HP in damage before mitigations, you are knocked prone.

Spells that deal knockback or pull also have the potential to deal poise damage and knock opponents prone. If a spell does knockback or pull, it does double its damage value to your Poise.

As a Reaction, players can Brace to stop themselves from being knocked prone.

Things that increase Poise

Constitution Modifier: Constitution Modifier raises the HP threshold by virtue of having more health

Armor Mods: Can negate poise knockdown

Things that halve your Poise

Difficult Terrain

Traps

Things that do double the Poise damage

Certain ammo types

Certain melee types