There is no way to compete with another guild except in guild war but there are 4 or more guilds involved. And the guild fight as it is now is not optimal.
instead of challenging a guild and fighting all over madrigal, the two guilds should be ported into some kind of arena/city map.
Area should be about the same size as kebaras maybe a little smaller.
Or you should then use kebaras as a battlefield because it's not being used anyway. And for the devs it's a matter of 10min to program it.
You could also make it so that the guilds post at 2 positions and each guild has a flag.
If you stole the opposing guild's flag and brought it to the base, the guild wins.
As an example the player picks up the flag and lands in the bag if he gets killed on it he loses the flag and stays there for about 1min if not it goes back to its old position.
You can make many game modes.