legion
This word carries a heavy weight of historical authority, evoking the structured, disciplined power of the Roman military. It suggests not just a large group, but a force that is organized, imposing, and potentially overwhelming. When used as a noun, it implies a sense of unity and singular purpose among many individuals. In its adjective form, it shifts toward a feeling of abundance that is often burdensome or chaotic. While a legion of supporters is positive, saying that one's troubles are legion suggests a scale of difficulty that is almost impossible to manage, creating a mood of exhaustion or awe.
Countable when referring to a specific military unit or a distinct group of people. Uncountable when used as an adjective to describe a general state of abundance.