Since this is still a writing tournament, only those who have entered may participate and to enter, you must have your own army. You may use other player’s characters as heroes in your army, but they should be written by the participant, not the original owners. While it truly is impossible to police this kind of collaboration offsite, we ask you try to keep as much of your posts as your own writing. You can ask the original owners for examples of personality, character traits, or links to other threads if you are concerned about keeping the borrowed heroes “in character”. Since these armies are so massive and there could be up to 24 of them, the events within would be difficult to assimilate into permanent canon. So, please keep in mind that there is a degree of creative freedom in how each writer uses said canon and how each writer wants these events to affect their own canon.
In short, the other players cannot write their characters as the heroes in your army, but you can ask them for pointers in how to portray them more accurately in your own writing.