Légendes is a french fantasy roleplaying game from the early eighties, set in 200 BC. The Celtic civilization (of which the characters are all part) is described in great details. The fantasy elements (faeries, druidic magic, mythological creatures) come from Celtic mythology.
The rules were quite simulation-heavy, and covered almost everything a character might do in her day-to-day life: hunting, sailing, riding...
The same ruleset was later used in other games, giving birth to the "Légendes" family of RPGs, as well as the "Premières Légendes" line (a simplified subset of these rules).