Tricholoma colossus

About

Tricholoma colossus, commonly known as Giant Knight, is a mushroom of the agaric genus Tricholoma. Due to its ringed foot, it was previously classified as Armillaria, even though it is otherwise clearly Tricholoma. The cap is 6–30 cm wide, brick red to chestnut brown, hemispherical when young, widening later on, uneven, always with very thick flesh, surface slightly sticky, developing somewhat into scales. The stipe is thick, 2–5 cm thick, solid. Ring-like formation at the top of the foot, above which it is white. It is considered a very rare mushroom that grows in association with pine trees.

Summary from Wikipedia