ok so the monster mash will require a few amendments to the standard rules of 40k as it is a bit of a special case.
well all take it in turns to activate our units based on the random number you pick. you can move shoot and assault as normal and then the next person has there go.
as it is all Vs all you are free to shoot into a close combat that is on-going, blasts hit what they hit while as non blasts shots are randomly allocated between combatants.
close combat will also change with you only making your attacks during you activation rather than at initiative.
imperial knights have to decide on the facing of there shields at the beginning of the turn before anyone activates.
any other things I need to cover?