I was just reading through the optional rules in the GM Toolkit and tried to make sense of the optional rule for spellcasting where difficulty is based on character rank versus spell rank. In the rule, a spell of the same rank as you is an Average Difficulty (2d) check. Which seems really weird. Because if you do not use this rule, same rank spells are, as far as I know, Simple checks (0d) unless they are opposed checks or "vs Defense".

So as far as I can gather, using this optional rule makes it MUCH harder for a starting wizard to cast spells. Am I reading this wrong?

The optional rule in the GM toolkit also says that this difficulty replaces the difficulty appearing in the action card; or if you want to make spell casting very difficult, you add it to the difficutly of the card

"These difficulties can either replace the difficulty modifiers listed on the
spell or blessing cards or (to make spells even more dangerous!) be
added to those difficulty modifiers."

Ah, I missed that. It was bit late when I read through the rules. It's still generally spike in diffiuclty though. But I guess it is considered a trade-off for later being able to cast spells as Simple Checks.

I think I'll keep the original casting rules.