Arkheim is split into four islands floating in the sky. These islands are only reachable by Ascension Gates that unlock at pre-set times called "Moon Phases" during the game round. You can preview these times in the World Map view.
Each island has its own map and slightly adjusted game rules, and with each Ascension to a higher one, the competition gets more fierce. To win the overall game round, you have to reach the highest Island before the endgame starts - but you can also ascend in your own time and compete on one of the lower islands for an island victory.
Very important: You cannot ascend alone - your Realm needs to work together to achieve that goal.
Once a Gate unlocks, it is occupied by Goblins you have to defeat to get it under your control.
Once you hold a Gate, your Realm needs to own enough Arcane Orbs to start and fuel the Ascension. It takes 12 hours to attune the Gate for the jump. Be careful: If Orbs are stolen and you sink below the required number, or you lose the Gate to another Realm during the ascension timer, the Ascension will be interrupted.
When the ascension timer is finished, your whole Realm will leave the current Island and your Ark will be placed on a new spot on the map of the next island. Your Orbs will be set to 0. There is a ring of Tower Ruins you can claim within the first 9 hours after the Ascension to help you rebuild your territory.
Half of the Towers you had on the previous map will be turned into Goblin Towers, the other half will disappear from the map.
Your Realm is now one step closer to Eternal Light. You will have access to higher levels for your Supplies and Towers. Most likely, you will also be closer to some worthwhile enemies, so prepare your Ascension carefully.