This is my suggestion for multiplayer free for all rules. I was going to post it in the multiplayer thread, but after writing it a bit I thought a new thread would make more sense.
Bidding: All players bid secretly and simultaneously. Then the players are paired. Players are always paired with the player either to their left or right. If there is an odd number, a 'leftover' player is chosen, whose bid is compared with a default bid of 3. The other pairings are determined automatically once the leftover player is known. If the same player is selected to be leftover in consecutive rounds, the selection is redone. If there is an even number of players, a coin flip can determine whether the first player pairs left or right, and this determines the rest of the pairings.
Victory: the game ends when any player reaches 25 honor or 0 honor, or when any stronghold is destroyed. If the game ends through a player being eliminated, the player to their right is the winner.
Rings: 2 sets of rings are used (10 total). No player may declare both attacks using the same ring if that ring was claimed during their first attack, even if another ring of the same type would otherwise be available. The exception is if a card effect makes the same physical ring they attacked with available again.
The rules below are to impose a bit of order on things: for a more anything goes experience the above rules are sufficient.
Attacks: Players may attack the player to their left without restriction. An attack against a player not to the left is a 'special' attack. Only one special attack may be declared against each player per turn. This means that once a player has had a special attack declared against them, no one else may declare a special attack against them for the rest of the turn.
Aid: Each player may recieve aid on defence from one other player once per turn. Both players must agree. For that conflict, the aiding player's characters may be assigned on defence. Aid is agreed to after the attack is declared. An aiding player may also play cards that specify that they must be used by a defending player or when defending your provinces as if one of their provinces was being attacked.
Edited by Eugene EarnshawAltered pairing rules for bids a little.