Monkshood
A striking blue-violet garden and mountain flower containing potent toxic alkaloids.
Conium maculatum
Русское название: Болиголов пятнистый
A highly toxic member of the carrot family. Other umbellifers can resemble it, making amateur identification especially hazardous. No part should be used as food or traditional medicine.

Do not use photographs or online summaries to identify wild plants for eating or medicinal use. Some poisonous plants resemble edible species and even handling certain species can cause harm. If poisoning is suspected, contact your local poison service or urgent medical care. Do not wait for symptoms.
Poison Control: poisonous plants (US) ↗Europe and western Asia; introduced widely
Roadsides, damp ground and disturbed soils
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.