For this achievement, you need to upgrade all the quests to the max level - on Emerald Island, this is level 100 - and ensure you upgrade your guildhalls too. Some of them you will have to set up. The guild halls are the grey empty squares on the floor later in the map, and the buildings you start with. To upgrade the guild halls completely, you need to upgrade each adventurer you have in the guildhalls, on both sections. When this is done, and all quests are at level 100, the achievement will pop.