Looking back over the die mechanisms I'd developed for Familiar, there was something that just didn't feel right. I couldn't quite put my finger on it, but there was just a niggling doubt in the back of my mind that the numbers just weren't working at some level.
So I've tried to consolidate some thoughts in the system.
Everything basically now comes down to even numbers. If a character's die misses the difficulty by 2 or more, the attempt fails completely. Otherwise it has varying degrees of success. Thus, there is always a chance of failing completely (however remote that chance might be). Similarly under most circumstances, there is always a chance at success.
Now, when a character draws on a metaphysical legacy, inherent skill/power, or item (mundane or supernatural) they simply add two points to their die roll. When advantages are at play, difficulty dice are decreased by a step (d12 to d10, d10 to d8, etc.) ...conversely, when disadvantages are at play, difficulty dice are increased by a step (d10 to d12, d8 to 10, etc.) If advantages reduce a difficulty die below d4, a d4 is still rolled, but the acting character sees their attribute die result increased by 2. If disadvantages increase a difficulty beyond d12, a d12 is still rolled but the acting character sees their attribute die result reduced by 2.
Another thing that I did for simplicity in the system was allocating 4 dice to the 4 attributes (a d6, a d8, a d10 and a d12), but this felt a bit contrived as I developed NPCs for the game. It also felt odd to advance characters away from this scheme...but then again there was no real advancement system for the game anyway.
Instead, I'm thinking of a template system to quickly generate characters. Choose a cultural template, a mystical practice template, and an elemental template. Each template increases an attribute or two, provides some specific benefit and possible weakness, and has a couple of options to allow for a more individualised character.