The Legendary Battle rules cater for games of more than 2 players fielding combined forces of 5000 pts or more per side (White Dwarf April 2008 WD340)
All the usual movement, shooting and combat rules apply but there are some added considerations taking into account the large nature of the game.
These new rules cover:-
1) set up
2) reserves
3) allies, common & occasional differentiation
3) magic power dice
4) monstrous 'hordes'
5) artillery batteries
6) desperation counters and
7) strategic objective points replacing usual victory point
I am digesting all the rules now and will write an update and review tonight.
The objectives points system looks excellent and quite inspired. There will be a lot for discussion though with the monster and battery rules.