Damage Types

Condensing the Damage Categories
5e has 13 types of damage. Many of them are superfluous, and have little meaningful or logical difference between each other. In this optional ruleset, they have been condensed into just eight categories. The purpose of this simplification is to allow any effects that utilize damage types to be more streamlined and easier to use.

Guidelines for DMs
Condensing damage types in this way can cause some minor issues with monster types.

If a creature had resistance or immunity to any of the damage types that form a new damage type, they have resistance or immunity to that new damage type.

Poison damage is an exception - if a creature has immunity to poison damage and no immunities or resistances to necrotic, it becomes resistant to toxic damage from nonmagical sources, instead of immune.

Less punishment, more reward
Damage immunities, vulnerabilities and resistances work somewhat differently within this new system.

Most creatures with immunity to a particular damage type are downgraded to lesser immunity (fiends, dragons)

A few creatures with bodies composed of a particular harmful substance (such as fire elementals or oozes) may instead have greater immunity to the associated damage type.

Creatures previously with resistance or immunity to nonmagical weapons instead have lesser resistance or lesser immunity to force and pierce damage.

Damage vulnerabilities increase damage taken by the vulnerable target by 50%, instead of 100%. DMs are encouraged to add additional damage vulnerabilities to enemy creatures where appropriate, particularly if a creature has many resistances and immunities.

Effects of Massive Damage
If a creature takes a huge amount of damage of a certain type from a single source, it may be subjected to an additional effect, as shown below. In order for such an effect to be triggered, the amount of damage must exceed a threshold equal to the creature's Constitution score + its level or CR (rounded down).

For example, a dire wolf (with a Constitution score of 15 and a CR of 1) would suffer an additional effect if it took at least 16 damage of a certain type from a single source, whilst a pit fiend (with a Constitution score of 24 and a CR of 20) would only suffer an additional effect if it took at least 44 damage.

Taking damage is not the only time such effects might be applied; the effects of certain spells and environmental effects might also apply certain statuses to a creature. For example, the wet condition can be applied whenever the creature comes into contact with a large amount of water, such as during a rainstorm, or after falling into a lake.