Is it inherently corrupting or is a code of behaviour kind of deal so the "corrupting weakness" effect can easily be removed in exchange for forcing the character to be really damn weird?
Eldritch magic and the corrupting effects are described not only in the Heroic Fantasy Companion but also in Axioms 1 which I highly recommend you check out if you haven't already.
Without giving away too many trade secrets: the gist is that magic is described in multiple shades, by which those with a code (such as eldritch casters) must abide. From there, the extent to which learning and casting certain shades of magic is corrupting depends on your setting and the corruption level you choose, from "tolkeinian" to "howardian" to "lovecraftian".
Hope that helps, and possibly entices you to try out Axioms1, it's great!
Edit: If you'll pardon me creeping on your post history, I see you already asked about Axioms 1. My understanding is that eldritch casters will adhere to a code of shaded magic very similar to the shaded magic described in Axioms1, so if you have that, you should have a good idea of what to expect.
Ah, yeah, I was wondering if it was a standard Code of Behaviour. I was hoping to put together a tribal shaman style caster using Eldritch magics without any of the corruption hassle.
IANAA but I believe adhering to shades of magic is always a code of behavior.
Hola! Here's how it works:
1. When a magic type is designed, it has various source modifiers that set the spell level of various types of spells for that magic type. For instance, Divine has a blast modifier of x2.25, while Arcane has a blast modifier of x1.0. That's why Fireball is a 3rd level Arcane spell, while the less powerful Flamestrike is a 5th level Divine spell. Conversely, Divine has a healing modifier of x1.0 while Arcane has a healing modifier of x1.5, which is Reincarnation is a 6th level Arcane spell even though its less powerful than 5th level Restore Life and Limb. Eldritch magic is mid-way between Arcane and Divine in its source modifiers; it's not as good at blast as Arcane, not as good at healing as Divine, and so on.
2. When a magic type is designed, it can either have a Code of Behavior, it can be free of a Code. If a magic type has a Code of Behavior, the magic type comes with class powers. Arcane has no Code of Behavior. Divine has a Code of Behavior and comes with Turn Undead. Eldritch has a Code of Behavior and comes with Spellsinging. The standard class power can be traded in for other custom powers if desired.
3. A particular type of Code of Behavior is called Shaded Magic. A Shaded Magic type has its Code of Behavior implicit in the magic. Eldritch has Shaded Magic. Shaded Magic means that casting certains types of spells under certain conditions causes corruption.
Hope that helps!
Ah, thank you both.
What, exactly, is Spellsinging?
Spellsinging is a method of casting eldritch spells that allows you to build the spell extemporaneously. I previewed it on a KS update on Tolkein Day.