Catan: 5-6 Player Extension on Boardgamegeek

Boardgamegeek https://boardgamegeek.com/boardgameexpansion/2807/catan-5-6-player-extension

English - Allows you to add up to two more opponents to The Settlers of Catan. The only change in the rules is that there is a building round at the end of each turn in which any player can build.