Changes

You can only cast magic up to the level of your sphere. Arete is added to the Sphere you are using to get the number of dice to roll when casting a spell. No Sphere can be higher than your level of Arete. You can also only spend up to your level of Arete in quintessence on a single spell. A mage can optionally roll fewer dice to avoid a potential potential botch.

The difficulty is the level of the sphere you are using. Add +4 3 difficulty for coincidental magic, and +5 4 for Vulgar magic, if there are no witnesses. +1 if a Sleeper witnesses it.

of Arete is at least one point higher than the level of the Sphereyou are using, you can succeed without a dice roll.