To claim an island you have to reach
8000 Points (you can see the points at the top of your screen, if you're on an island where the war is active) or the time is up when you have the most points out of all aliances which are at that point on the isle. There are multiple options to gain points:
Target | Reward |
Occupy All Fortresses | For every Fortress you claim you get 300 Points instantly. Also you will get points over time. These points will be added to your point pool as long you own the fortress. |
Occupy The Zitadelle | The Zitadelle does't give you 300 points instantly, but it will give you 50 points / min (when you own it) which is the same as all fortresses togheter (over time). |
Crystals | You can gather Crystals all over the map. You can have a max of 102 crystals at once. If you hand the crystals over at a Allied Fortress or the spawn point, you will get the double amount of points as you had crystals. Keep in mind, if you get killed by a player you will lose half of your crystals and the enemy player gets it. |
Its optional to get the altar. If you get it you will get a buff which gives you 5% HP for five minutes. If you're the captain (you got on the island first from your alliance) you wil also get the possibility to spawn the legendary dragon. As long as you do not spawn the dragon you will also get an permanent HP buff.
Most people just keep the dragon so they can profit of the amount of HP they get.
Hope that helps.