Combat in Nobilis is absolutely discouraged, mainly because it's more a social game than a combat aligned game. But this doesn't mean combat is non-existent.
Nobles, Swords and Blood
The official rule book contain only brief instances of how combat should be handled. But in general line, physical attacks are hard to connect and projectile attacks are dodged effortlessly by anyone with an Aspect 2 or more. As for Miracles and other magical effects, the only way for them to miss is by countering them of hoping your Auctoritas bounces them off (which is rare since the Hollyhock God as access to your Spirit value).
Because of this it's advisable to use house rules to simulate combat, especially when players are eager to kill every mortal they can see going against their interests if off course Lord Entropy doesn't mind at all you kill them. Nothing stings more than an angry Overlord of all Cosmos (and this is often used in Nobilis Lore focused campaign to hinder players, and stranger enough, it actually works).
Turn Based Combat
to be added
Active Time Combat
More commonly used in Nobilis games, this allows less discussions and more enjoying of the game, but in return creating a more chaotic environment where every one does what they please when in combat.
Miracles, counter-Miracles, counter-counter-Miracles and combat combos that could flinch and pin down Hulk Hogan in three seconds are the most common actions players tend to make in this sort of combats. That is, if the Hollyhock God isn't doing her job properly.
Just like any soccer match, this of combat requires both parties to act calmly and give time so that each happening events can be sort out. For this there a couple of rules to be taken into consideration. And that set of rules is the Stack Law.
In current time combat, actions take place in the order they are imputed. That is "first to come, first to serve". When a group of multiple actions want to happen at the same time they form a stack. Stacking actions allows them to happen with little conflict with each other and in case of discussion it eases the process of figuring who's right.
For example, if Rodgort the Rotaninrub casted a Fire Spell and after that Rurik tried to swing his sword at the wizard, then the spell would burn Rurik first and then if is capable he delivers his swing.
Actions always happen in the order they are announced, if they have a "physical" target. If, by some fate of chance a player targets another action (it's possible), the the stacking rules allow those two intertwined actions to happen at the same time. This is only possible when those two actions haven't happened yet.
For example, if Rodgort the Rotaninrub casted a Fire Spell and Rurik prepared to Parry if with his shield, both actions would happen at the same time.
Off course this only discusses how actions and events are to be treated. Their effects are entirely up to the Hollyhock God's imagination.