Elements

NeoForge 26.1.2 and 1.21.1.

An element is a damage type or a damage type tag. Wherever a field takes elements, it takes one string or a list:

Written	Means
"minecraft:magic"	hits of that one damage type
"#minecraft:is_fire"	hits of any damage type in that tag
"#fundamentum:element/fire"	the same, and also hits that are fire through their weapon (a weapon in the item tag #fundamentum:element/fire)

Fundamentum's elements are fire, soul fire, ice, water, electric, earth, air, poison, holy, shadow and arcane. Each is a damage type tag #fundamentum:element/<e> and a shared damage type fundamentum:<e> that any mod can deal.

Element	Tags	Shared damage type	Variant of
fire	#fundamentum:element/fire	fundamentum:fire
soul fire	#fundamentum:element/soul_fire	fundamentum:soul_fire (burn ticks: fundamentum:on_soul_fire)	fire
ice, water, electric, earth, air, poison, holy, shadow, arcane	#fundamentum:element/<e>	fundamentum:<e>

Names shown in game come from lang keys element.<ns>.<path> with / as . (element.fundamentum.element.fire).

Variants: soul fire is fire

An element can be a variant of another (its parent). Every hit of the variant also counts as the parent, so anything that checks the parent covers it; the variant only adds to it. Soul fire is a variant of fire: fire resistance, fire-immune mobs, water and frost putting it out, fire auras and every fire reaction apply to soul fire unchanged. On top of that, soul fire sets what it hits burning with blue soul flames (2 HP a second instead of 1), and has its own reaction and affinities below.

For damage types the variant's tag sits inside its parent's: the damage type tag #fundamentum:element/fire lists #fundamentum:element/soul_fire, and fundamentum:soul_fire and fundamentum:on_soul_fire are in #minecraft:is_fire, so anything that checks those tags counts soul fire hits too. The item tags are separate: the item tag #fundamentum:element/fire does not list the soul fire one. A weapon in the item tag #fundamentum:element/soul_fire still counts as fire, because Fundamentum's element check (Element.matches) covers a parent's variants in code. Code adds a variant with Elements.variant(id, parent, damage, resistance) (see the API).

Soul fire

• Burning blue. An entity set on fire by a soul source burns with vanilla's soul fire sprites (third person and the first-person screen fire, the same render path as vanilla fire, so shaders treat it the same). It goes back to orange or out when the fire ends, when it touches ordinary fire or lava, or when something non-soul sets it alight.
• Sources: blocks in #fundamentum:soul_fire_sources (soul fire and soul campfires), projectiles in #fundamentum:soul_fire_projectiles and melee weapons in #fundamentum:soul_fire_weapons that set targets on fire (Fire Aspect, flaming arrows), and every hit of the soul fire element (it sets the target soul-burning for 4 s).
• Damage: 2 HP a second while soul-burning, the vanilla soul fire block's contact damage. Config config/fundamentum-soulfire.toml: soulFireBurnDamage (default 2.0) and soulFireHitIgniteTicks (default 80).

• A soul weapon, data only: put the item in #fundamentum:element/soul_fire and its hits are soul fire (and so fire). To keep a weapon's hits as they are and only turn the fire it sets blue, use #fundamentum:soul_fire_weapons instead. For example data/fundamentum/tags/item/element/soul_fire.json:

  {"values": ["mymod:soul_blade"]}
  

Auras

A hit leaves an aura of its element on the creature it hits. Data map on damage types: data/<ns>/data_maps/damage_type/element_aura.json. Keys are damage types or #tags.

{
  "values": {
    "#fundamentum:element/fire": {"aura": "#fundamentum:element/fire", "strength": 1, "duration": 120, "decay": 0, "max_stacks": 3, "min_damage": 0},
    "minecraft:drown": {"aura": "#fundamentum:element/water", "duration": 200}
  }
}

Field	Default	Meaning
aura	the damage type itself	which aura the hit leaves; point many damage types at one shared aura
strength	1	strength added per hit (capped at strength * max_stacks)
duration	100	ticks the aura lasts; every hit refreshes it
decay	0	strength lost per second; the aura ends at 0
max_stacks	1	stacks it can build up to (one per hit)
min_damage	0	hits below this leave no aura

Reactions

What happens when a hit of one element lands on a creature carrying an aura of another. File: data/<ns>/fundamentum/element_reaction/<name>.json. trigger and aura are required.

{
  "trigger": "#fundamentum:element/fire",
  "aura": "#fundamentum:element/ice",
  "priority": 10,
  "exclusive": false,
  "min_stacks": 1,
  "consume": "all",
  "apply_trigger_aura": false,
  "damage": {"multiplier": 2, "bonus": 0, "per_stack": 0},
  "convert_to": "minecraft:magic",
  "effects": [{"id": "minecraft:slowness", "duration": 60, "amplifier": 1, "on": "target"}],
  "knockback": {"strength": 0.6, "up": 0.2},
  "ignite": 0,
  "extinguish": false,
  "burst": {"radius": 3, "damage": 2, "scale": 0.5, "damage_type": "fundamentum:electric", "include_target": false},
  "fx": {"particle": {"type": "minecraft:cloud"}, "count": 12, "spread": 0.4, "speed": 0.02,
         "sound": "minecraft:block.fire.extinguish", "volume": 1, "pitch": 1},
  "function": "mypack:on_melt"
}

Field	Default	Meaning
trigger		the element of the incoming hit
aura		the aura it must find on the target
priority	0	several reactions can match one hit; they run from the highest down
exclusive	false	true stops the reactions after it
min_stacks	1	aura stacks needed
consume	all	what it takes from the aura: all, one or none
apply_trigger_aura	false	whether the hit still leaves its own aura
damage	x1	multiplier, then bonus, plus per_stack for each aura stack
convert_to	none	the hit becomes this damage type (and reacts and resists as that type)
effects	none	id, duration (100), amplifier (0), on: target or attacker
knockback	none	strength (0.5), up (0)
ignite / extinguish	0 / false	seconds of fire / put the fire out
burst	none	damage around the target: radius (3), damage (0) plus scale x the hit, damage_type (minecraft:magic), include_target (false)
fx	none	particles (any particle JSON) and a sound
function	none	a datapack function to run

Chains can't loop: a reaction never fires while it is already running, never twice on one creature in one tick, and chains stop 8 deep.

Affinities

Resistances, weaknesses and immunities. The same shape is a data map on entity types (data/<ns>/data_maps/entity_type/element_affinity.json) and an item component, counted while the item is worn or held:

{"values": {"minecraft:blaze": {"resist": {"#fundamentum:element/water": -1.0}, "immune": ["minecraft:drown"]}}}

/give @s diamond_chestplate[fundamentum:element_affinity={resist:{"#fundamentum:element/fire":0.5}}]

resist values add up over every matching entry: 0.5 takes half, -1 takes double, 1 or more is immune. immune cancels matching hits outright. Items with the component show it in their tooltip.

The vanilla set

A built-in datapack, Fundamentum: vanilla elements, is on by default. Turn it off with /datapack disable "mod/fundamentum:packs/elements_default".

Reaction	Hit on aura	Result
melt	fire on ice	x2
quench	ice on fire	x1.5, puts the fire out
vaporize	fire on water	x1.5
freeze	ice on water	+2, Slowness IV 3 s
electrocute	electric on water	3-block burst of electric damage, the water stays
overload	electric on fire	2.5-block explosion burst, knockback
detonate	explosion on fire	x1.5, takes one fire stack
shatter	explosion on ice	x1.5, turned into magic damage
blight	shadow on arcane	x1.25, Weakness 5 s
smother	water or drowning on fire	puts the fire out
soul_rend	soul fire on shadow	x1.5, soul particles

Soul fire also sets off every fire reaction above (melt, quench, vaporize, overload, detonate, smother), because it is fire.

Its affinities: undead resist shadow and are weak to holy and soul fire (-0.25); vexes and allays resist soul fire (0.5); the Warden is weak to it (-0.5); blazes take double water; endermen take more water; guardians take more electric; polar bears resist ice; snow golems are immune to ice and weak to fire.

Test with /fundamentum element (see Commands).