Sanctuary Treasure Chest
Check the treasure room and you should see a golden key by the ceiling. The only way to reach it is by earning at least 5,000,000 gold. (See this guide's money trick to know more how to earn millions in minutes!) Once you have a mountain-pile of gold, grab the key, then get rid of those gold either by temporarily donating it to another player or transferring to the kingdom treasury (the latter requires you to become the ruler of Albion first). Once the treasure room is cleared out, you'll find a chest by the wall. Open it to get a Legendary weapon!