Some new game mode ideas here
I think many new games modes should be developed instead of just this one War mode. In these examples I will use a 10 on 10 match.
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Dominance
There will be one map filled with Goblin bases. The Goblin bases will be equally ranked versus the players. So a rank 1 Goblin base will be like PEKKA's Playhouse or equivalent and a rank 10 will be like Goblin Forest or equivalent. You may have to make the bases generate randomly so nobody can figure out a easy win for it.
The object then is for players on both sides to attempt to take over each base by getting 3 stars. Each player gets 2 attacks (or more depending on what level of Dominance you want to play, quick = 2 to long = 5). When a player takes over a Goblin base, their base takes over (or you can just have the Goblin base change color to the winning clan, but I like the player's base taking over better). That means the other clan needs to attack it with 3 stars to take it over.
The clan that controls the most bases wins. Players can make multiple attacks, but if they win while they've already controlled a base, their base is moved to the new spot and the old base goes back to the Goblins.
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Attrition
Set up like the current Clan War. Players are allowed a certain amount of resources based on their level, town hall, or current stockpile. I would recommend that higher level players receive less resources than the lower leveled players. This will need to be figured out, probably playtested.
Players are allowed to attack as many times they want utilizing only the resources given to them at the beginning of the match. The object to gathering stars. Bonus will be based on the number of stars you collected.
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Invasion
First day is preparation day. All players will donate for defense AND donate for the attack. The donation for defense will be the same as the current Clan War. Donations for attack works a bit different. Players are allowed to donate as much troops as they want, whether it be 1000 barbarians, 50 dragons, etc. This is all up to the clan. I would probably max out the donation of each player to 1000.
On Invasion day, all troops that were donated will then begin to attack the opposing clan in waves. The waves will be based on housing cost. First wave can be 60, second can be 120, third would be 240, fourth would be 300, fifth would be 360. The wave is not complete until the troops are eliminated. A player can control it going against the enemy clan of the same rank. That means if I'm ranked 5, I can control what is deployed against the enemy clan's ranked 5 player. The troops deployed will be taken from the pool of donations. That means the players need to coordinate or manage the waves to some degree. Before the wave starts, the player can choose what troops will be deployed and then gets to deploy them. Give them 2 minutes max between waves. If nothing is selected, then the wave is won, and so on until wave 5.
Players are awarded 1 star for every wave they survive. The clan with the most stars win. You can max out the waves to 5.
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Feel free to comment on how to improve it or say whether you like them or not.