Pax Artica Achievement
Complete a multiplayer match without having one of the players left tileless.
This achievement requires that you complete a multiplayer game without having any play left without a colored tile. This is fairly easy to do as it doesnt matter who wins the match and this occurs quite frequently without even trying.This will require some luck, but basically your strategy is to avoid destroying colored tiles belonging to any opponents. If you have a second account playing, it will help a little but it is definitely not needed. Just focus on not destroying any tiles with that account as well.