YAS!!!!!!!!
Kendama and affiliates approve this message.
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However, this whole warping to battlefield sounds unnecessary and people would abuse it to warp out right before they die.
What would be better is if it focuses on the overworld. My example is going to be with Voyage and SoN.
Some things should be some things you set up before the war.
On the "declare war" page, once you have chosen which guild you are declaring war on, you need to set up how long the war will last, if allies count, and anything else.
Say I declare War on SoN and they accept the challenge. All of SoN will now have red arrows (like the green arrows above guildmates) to people who are wearing Voyage tag. It is a simple counter for each guild how many kills they can rack up on the opposing one.
At the end of the time set for the war, the winning guild should receive something. It shouldn't be anything like gralats or a prize, but it could be used for a new statistic page on the guild page. Like, you go to Voyages page, and there is a button that says "view war history". You can view all of the wars between Voyage and what the outcome was.
Just for a more interesting concept, perhaps while setting up the war rules you can chose more than one guild on each side of the fight. Could be allies or whatnot.
Exa: Voyage and Maphasy, vs, SoN and NaL II.