Goat format ruling
Dark Room of Nightmare

Card effect (current official text)Each time your opponent takes damage from a card effect, except "Dark Room of Nightmare", inflict 300 damage to your opponent.
Rulings
- A cost is not damage so this card’s effect does not apply against Chain Energy, or costs for Imperial Order, etc.
- Q: Would the opponent receive damage from "Dark Room of Nightmare" when losing LP from the effects of "Toll" and "Chain Energy"? A: The effect of "Toll" and "Chain Energy" is not damage, so "Dark Room of Nightmare" will have no involvement in those card’s effects.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Goat forum — sourced change requests get reviewed.