Some additional findings based off the post and video linked by @greyhiem
Chortasmata does increase immolation and fanatic illusion damage. The increase via % feels weird, anyone can shred light to this? The build used for testing is C2Krivis3Druid2Zealot2. There isn’t any diev in the build so the +20% to plant is ruled out. Does plant type takes in more damage from physical damage? How is it calculated?
Damage is based on 699patk flat (no weapon to eliminate min-max damage), no addon cards or blessing buffs. +1k fire damage attribute from immolation is turned off.
Without Chortasmata
With Chortasmata
That’s roughly a 8% increase in damage.
Fanatic Illusion also increases too roughly 7+%, without grass
and with grass
The strange thing is on different monsters. the damage increment is different. It does 12.5% for both Immolation and Fanatic Illusion on the Kugheri below: