Knowledge skills house rule - Planescape related

[Li Shenron]

Remember - the other knowledge skills are pretty broad too. Knowledge(local) isn't actually restricted to a certain area - it's just used to know things about cities(ANY city), ordinary people and legends.

That's how it seems from the PHB, but WotC books use Knowledge(Underdark) for example and some others as well I guess...

I think it would make sense to have one knowledge for each plane in a setting like Planescape, although I agree that it is very inconvenient for the characters. There could still be a generic Knowledge(The Planes) used for example for questions like how to shift from plane to plane, which magic cross plane boundaries, how planes are born, and definitely gives synergy bonuses to all the specific knowledges of single planes.

One more thing: remember that every knowledge can be used UNTRAINED, only that you are restricted to common knowledge (DC 10 or lower), but it is actually up to the DM to decide what knowledge is common in a setting where everyone is planehopping around the universe For example, it may be common in Planescape to know that city X is on plane Y, that plane Y has dead magic zones and its people are immune to fire; it would take Kno(Y) to know the location of dead magic zones on Y, the best shops in X, and that fire immunity of the people can be suppressed with a special use of the spell Z.

 

[Dakkareth]

I like this take on the situation - different knowledge skills for sets of planes and synergy boni on planes belonging to more than one set. I'd definitely give the PCs a certain number of skill points per level to spend exclusively on these skills.

I do think however, that there should be one (or two) general skill(s) representing general knowledge - like what a tiefling is, how to get around the planes and at the higher levels for the planar mechanics, ie the metaphysical structure, strange effects, etc.

In short, I'd keep the Knowledge: The Planes skill for all general things, but in order to know the location of the Sinker's citadel on the negative energy plane, you'd need to have an epic number of ranks - or a couple of ranks in Knowledge: Inner Planes.

This way, the wizard would still be the one to know all the bizarre stuff and metaphysical mechanics of the planes, while only the barbarian knows how to find his way through the Abyss and how to deal with the creatures of the Outlands.