If you’re his servant or a freelance adventurer living with Isan and you have no magic, you get this text:
While the wizard himself does the specialized, highly delicate work of spellcasting, you are the one who must ensure he has all the spell components, notes, equipment, and required artifacts on hand for each casting. Most of your days are spent running around the tower as Master Isan inundates you with a constant stream of demands and questions.
It doesn’t take you long to pick up the basic concepts of what you are working with, both from the wizard’s own hurried explanations and your observations of your master at work.
That gives the basics of peace magic, which means that it’s possible (though perhaps very unwise) for anyone staying with Isan to choose Isan’s plan. If you’re Isan’s new apprentice (because you chose that reward in the previous chapter) and your will is below 4 and/or you have basic magic at best, you get this text:
As his apprentice, you are expected to use your magic alongside his. He has you cast the simpler and less powerful spells while he concentrates on the more complex casting his research requires. Day after day, you spend hours casting the same basic spells over and over again. It is absolutely exhausting, but it hones your will to a fine edge. Your knowledge, too, grows swiftly under such uncompromisingly intense spellcasting. Soon, the spells that had seemed so alien and mysterious to you now become mundane, their casting almost second nature.
A new apprentice gets more out of this than a servant if their will is less than 4 or if they have the basics of peace magic already. Unfortunately, @Pheriannath’s character fit neither of those categories, so the only benefit he got from becoming Isan’s apprentice was the possibility of being named a (woefully underprepared) Court Mage.
Only someone with Dame Mildred as mentor ends up poisoned, which means that prowess was boosted from training under Dame Mildred before being lowered. Isan detects a poisoned cabbage, which protects someone with Isan as mentor, someone with William as mentor buys the writ automatically, and perhaps William doesn’t think a freelance adventurer is worth poisoning (stealing their money or slandering their reputation instead). If the MC starts with 5 prowess and is Dame Mildred’s squire, then the prowess boosts are capped when the MC reaches 6 prowess, and then loses 2 prowess from the poisoning, ending up at 4 prowess and 2 in every other stat. (Dame Mildred’s servant only gets 2 prowess boosts, unlike the squire’s 3, but they aren’t capped at 6, so a servant who started at 5 prowess would go up to 7 and then back down to 5 from being poisoned.)