Death cap
Contains amatoxins that can cause life-threatening liver damage.
Galerina marginata
Русское название: Галерина окаймлённая
A small brown wood-growing fungus containing dangerous amatoxins. Many little brown mushrooms resemble one another, and visual shortcuts are unreliable. Suspected ingestion warrants emergency medical advice even before symptoms.

Never decide to eat a wild mushroom from a photograph or online description. A mistake can be fatal. For mushroom ingestion or suspected poisoning, contact emergency medical services or a poison centre immediately, even if symptoms have not appeared.
Irish Poisons Centre mushroom safety ↗Temperate regions including Europe and North America
Decaying wood, logs and woody debris
Images and brief descriptions are for learning, not for reliably identifying a specimen. Take particular care with poisonous plants and mushrooms.
Identification is never guaranteed by a photo. Scientific names are used to reduce confusion between local names.