Voadam said:
However his solution seems nonsensical.
If you just shift that ability into the description section then you will create a disconnect of description and mechanics.
What you will have is something that does not affect PCs.
This could be a problem. I could see a PC killed by a shadow. It doesn't say he spawns in that encounter, so he doesn't. Maybe the DM will decide he does - he's got that authority, specifically, the authority to add another monster to the combat. But what happens when the PCs try to use the Raise Dead ritual on him?
Is he dead, or not?
This is why I think
players should be able to initiate skill challenges. If they can, there's no problem. "We want to use Raise Dead." "No - he's not dead." "Okay, then - skill challenge: can we get him to the state where we can use Raise Dead on him?"
In my view, the role of fluff is to frame a conflict. In the shadow spawning case, it does a great job of adding to the dead character issue. Not only do you have to spend your Ritual resources, but you have to succeed at a skill challenge as well. (And if you succeed, you get XP. Important!)
But if it's only up to the DM, there could be arguments. If you can agree to let the dice settle it, and everyone has the option to say, "Let's go to the dice", functional groups should be okay. (And I think functional groups could still have that argument - "No, no skill challenge here, sorry guys, he's not dead" - if the authority rests in only one person. Maybe I'm wrong, maybe functional groups don't need that.)
Voadam said:
If there are no mechanics for spawning the default would be no spawning, that they'd need to be individually created somehow just as mummies, zombies, skeletons, and liches must be.
That's just not true. The DM can say something happens without having to use mechanics to say it does, just like I can say my PC has red hair without having to roll on a table. There aren't any human reproduction mechanics, yet life still goes on.
What you
do need mechanics for is resolving conflicts (in 4e, at least how I think it is designed to be played) between PCs and "the world". If you don't want PCs to become shadow spawn if they are killed by them, then don't let shadows have that ability. That says nothing about how shadows can affect NPCs.
Voadam said:
If shadows spawn instantly this must be clear beforehand because it will significantly impact encounters with shadows.
Very true. If you don't want them to spawn PCs, don't let them.
Voadam said:
I want powers described enough for me to use them meaningfully in encounters and I want the descriptions to match the mechanics.
If the shadow spawn ability stands as it is, no mechanics, you can still have the description match what happens in the fictional world as resolved by the dice.
I think you know how I would play it - either the PC spawns as a Shadow (if I, as DM, think the encounter could use some more spicing up) or he writhes in agony, about to become a shadow, out of the reach of divine intervention - unless you succeed at a skill challenge, that is...