Spell Gem Damage modifier

I tried to figure out the damage modifier for single target and AoE spells.

Test setup was like this:

  • made save backup
  • drank Potion of Forgetting (to remove outgoing damage and int)
  • discarded all cards
  • equip nether with morph spells to ensure that the caster is not strong/weak against the enemy
  • equip damage gems on my death and life creature (make sure no gem has a damage bonus)
  • go to realm level 1 and kill the enemy creature with a spell (lookup its defense in the bestiary)
  • write down the damage number from floating combat text

Here is the raw data:Spell Target Defense Int Damage Multiplier1 Multiplier2 Heaven's Thunder Psychic Vortex 16 1242 1858 1.508856683 1.515497553 Medium Single Blistering Radiance Humlitas Sanctus 14 1242 1651 1.34057971 1.344462541 Large AoE Blistering Radiance Harpy Hag 12 1242 1675 1.358293076 1.361788618 Large AoE Blistering Radiance Canopy Arachnalisk 13 1242 1659 1.346215781 1.34987795 Large AoE Finger of Death Brownie Enforcer 15 207 575 2.850241546 2.994791667 Massive Single Finger of Death Griffon Divebomber 16 207 571 2.835748792 2.989528796 Massive Single Finger of Death Anguish Banshee 23 207 549 2.763285024 2.983695652 Massive Single Finger of Death Tormented Banshee 147 207 122 1.299516908 2.033333333 Massive Single Finger of Death Raven Acolyte 128 207 156 1.371980676 1.974683544 Massive Single Rightous Storm Volcanic Efreet 8 1242 1152 0.9339774557 0.9335494327 Small AoE Rightous Storm Unicorn Consecrator 16 1242 1139 0.9299516908 0.9290375204 Small AoE Murder of Crows Disciple Occultist 11 207 322 1.608695652 1.642857143 Medium AoE Murder of Crows Pit Worm Gladiator 17 207 311 1.584541063 1.636842105 Medium AoE Murder of Crows Whispering Shade 16 207 312 1.584541063 1.633507853 Medium AoE Holy Explosion Waspid Hiveleader 11 1242 1403 1.138486312 1.139723802 Medium AoE Holy Explosion Medusa 11 1242 1403 1.138486312 1.139723802 Medium AoE Holy Explosion Imp Hexer 7 1242 1411 1.141706924 1.142510121 Medium AoE Finger of Death Leda Imling 1 207 623 3.014492754 3.024271845 Massive Single Murder of Crows Leda Imling 1 207 343 1.661835749 1.665048544 Medium AoE Cloud Beam Magma Golem 26 1242 1126 0.9275362319 0.9259868421 Small Aoe Heaven's Thunder Winter Aspect 13 1242 1870 1.51610306 1.521562246 Medium Single

Multiplier1 is (EnemyDef + Damage) / CasterInt => this was the logical way to compute the multiplier for me: increase CasterInt by a multiplier and reduce it by enemy defense
Multiplier2 is is Damage / (CasterInt - EnemyDef) => this would mean that you first reduce your CasterInt by the enemy’s defense before applying the multiplier which seems counterintuitive but has less derivation between different spell casts. From the way the data fits Multiplier2 I would guess that this is the correct formula.

For the last two casts I buffed the enemy level 1 creature with Bone Armor increasing its base defense by 128. The results when casting Finger of Death were … odd. From a pretty obvious 300% multiplier Finger of Death dropped to a 200% multiplier. I do not have an explanation yet.

Anyway here are some (likely) multiplier for the different spells:
Finger of Death: 300% (except when it isn’t)
Murder of Crows: 160%
Rightous Storm: 93%
Holy Explosion: 114%
Cloud Beam: 93%
Heaven’s Thunder: 151%
Blistering Radiance: 135%

The multiplier are still strange and should be much closer together. It is possible that the formulas might be wrong (the strange behavior of Finger of Death against a high defense target suggests this) but I have no idea what could be a factor. If someone has any idea how to explain the difference or another formula I can try let me know.