When your items run out of Ammo, Regen 10 » 20 » 30

The first time you fall below half Health each fight, gain 1 » 2 times your Regen.

You have +25 » +50 Regen for each Frozen or Slowed item

When you use a Food, Slow it for 1 second and Regen 3 » 6

When you use a Friend, Regen 2 » 4

You have +3 » +6 » +9 Regen for each non-Weapon item you have

When you Burn, Regen 2 » 4

You have +Regen equal to half the Burn on an enemy

When you Poison, Regen 2 » 4

The first 5 » 10 times you use a Chilled item each fight, Regen 10