How does one get to the NeverNever?    I know there are rituals and doorways, but how will it be handled in the game?
 
And few other questions: 

How does topography match up?   Example:  If I leave an area of plains in the Prime Material, will it be plains on the other side?  (Yeah, I know it's magic and they can end up anywhere, but generally speaking...)

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How many different dimensions are there?   If each religion/philosophy has a metaphysical afterlife or state of being, you could have numerous destinations.    Not to mention, how to "fit" them all in, is the Prime Material a focal point with all the other dimensions dividing it?   And what about a "cosmic pecking order"?  Which dimension would trump what dimension?  (Not asking for a ranking, but more an idea of how the power/space is shared and mapped out.)
 

 

How are you going to implement these in games?   You are sure to have player characters fighting against NPC wizards, so how are you going to keep curses a real threat without ruining game play for the cursed players?
 
How much "power" does a death curse have?   Can they warp reality on a major scale?  Example:The curse erases the memory/records of a person's existence from the world.  Or is it more limited?  Example:For each day that passes, the cursed ages one year.
 
Or is it a matter of the power level of the cursing wizard?