I was wondering if this would come up.
Harp Core, page 84, second column:
With this system, players are required to roll Initiative each round due to changing conditions...
In Our group (Our house rules), we decided that this was extra dice rolling that we didnt want, so we roll at the start of combat and keep the same initiative order, unless we hold actions, etc..
This has the problems that we can hear what everyone else is doing and it is hard to keep "player knowledge" about what is happening in combat separate form character knowledge. We solved this mostly by giving everyone the Earrings of Association, thus everyone gets a "bonus" to combat...
It also means that one round spells cant be interrupted...
This applies to NPC's as well as PC's though... This was very clearly defined during the time we decided upon the house rules.
IN the standard combat, everyone decides what they are going to do first, then they proced to roll initiative meaning that a fighter that is hidden from the mages view, may run at the mage last in the round. Next round he rolls initiative and goes first, getting to attack and stun the mage - preventing casting of any attack spell. Utility/defense spells are at -50 too remember (the stun rules, page 95)
Finally, remember that you are supposed to declare actions BEFORE you roll initiative.
So a mage declares he is casting a spell and has no idea what the NPC's are doing unless he wants to also declare that he is using a combat perception to spot what is going on.
(As spells require the user to concentrate so much on forming the sigil, this can be debated to mean that if he fails this combat perception that he doesnt see the warrior charging at him at chi speed mode!)
So he is taking a chance that he will roll an initiative whose end result is higher than the enemy he is facing. if the enemy gets to attack him first he has three options: Cancel his 1 round spell and Sudden dodge; or cancel his 1 round spell and cast an instantaneous spell (bladeturn is a favourite!); or ignore the attack and hope his DB is good enough to deflect all damage (otherwise pg 109 takes effect and he looses the spell and PP).
Again, house rules on how you roll initiative for combat are extremely important in determining if mages can cast 1 round spells with immunity.
I hope this explains the reasoning behind it. And good luck deciding what house rule you wish to follow for even deciding to use the books word for word is still a house ruling. Deciding to use COM or ML is a house ruling. Some of these rules dont gell (such as using MAFG with HARP core monsters, or Codex with HARP core spells: re: Control Animal).
Everything is a House Ruling!
If