What are the limitations and penalties of going on a murder spree?

As my time in Amalur wound down last night, I decided to do the only logical thing and murder everyone I came across. I managed to make mincemeat of most of a village of Fae, but then I encountered someone who had a quest indicator over their head. I couldn't do damage to them, and talking to them seemed to indicate that they were still regarding me as a "friend" and that they still wanted my help with a quest.

(This was despite the fact that I was repeatedly bludgeoning him over the head with a magical staff of burning things with fire that was soaked with the blood of their compatriots, but I digress.)

It seemed I was able to take out most of the "non-essential" NPCs in an entire town this way, and I wasn't once stopped by a guard or other law enforcement individual. Further, there was no reaction from the citizens spared on account of their relative immunity to my attacks.

What are the limits to my murderous rampages? Can I kill shopkeepers? Does it matter if they're "generic" villagers or they have unique names? Are there any side quest NPCs that I can murder?

Further, what are the consequences? Will I be caught and sentenced to 2 minutes in prison at some point? Is there some "faction standing" that I tanked during this?

Solution 1:

You can kill almost anything except main quest givers. Side quest givers are a hit and miss because the ones you ARE able to kill will have a fate-like essence surrounding them. That means they will revive. Some will never die and continue to revive and attack you. An example is the first city you get to in the plains where a side quest giver is collecting arm bands. Attack him and everyone else and you will see what I am talking about. Guards are also unlimited and always seem to match your level in some way. If you resist arrest it takes a very long time for them to cool down so to speak.

Solution 2:

KoA: Reckoning is, at its core, a single-player MMORPG. The only consequence of going on a killing spree is to have the town guards arrest you. You can choose to bribe them, serve your sentence or break out of jail, which will have absolutely zero effect on the villagers or any faction.

When it comes to killing NPCs, I believe you can kill them as long as they don't have a quest to give you. I haven't tried killing side quest givers, so don't take my word for it.