A Sixth city deed is required to build your sixth city. You can either buy this deed from the shop for 850 gems or you can collect the following crests to receive the deed:
- 4 King Arthur's Crest
- 3 Morgana's Seals
- 2 Mordred's Seals
After you were granted your Sixth City deed, you are also rewarded a highly valuable Divine Inspiration for your future building purposes.