The Last Bastion...
Orders have arrived from the alliance higher-ups to send a team of twenty, and everyone in the team should be Rank-6 or above. No one below that rank was allowed to be a part of the team.
The Alliance didn't waste time after they made a plan. They immediately sent orders to the three places from which they were going to draw some personnel for the mission.
They were afraid that if they took too long, the Supreme from the Cult might take whatever was present there.
The supreme is said to be the most powerful one in the cult, and for him, the alliance has prepared a plan to catch him if possible. If they can catch him, they can end the cult and this war with them. This would give a lot of breathing room for the alliance.
Once the internal threat was taken care of, external threats like the monsters would be easier to deal with, but the alliance knew that might not be 100% possible. There would always be someone who would think that they are above everyone else.