Solution here is
Invite more players, Create more Guilds
The problem is that BIG Guild tend to benefit more with lesser guilds choosing to ally with the current holder of biryu
Create more options/guilds so more alliances can be formed
TEMPORARY SOLUTION, my suggestion:
Biryu will be CLEARED after war, meaning whoever alliance who captures it for the night will get their respective prizes BUT come Sunday, BIRYU will again be open for all, NO OWNER/S so all guilds will be free to register on their own and ally on their own
The other guilds tend just to register under the defenders, so until such time more guilds are formed, I think this can be useful