Expanded Arcane Spell Acquisition Rules for Advanced Old-School Essentials

Old-School Essentials (OSE) and 1980s "basic" D&D restrict magic-user spell acquisition to mentoring and research, as described here:

https://oldschoolessentials.necroticgnome.com/srd/index.php/Spell_Books

Notably, magic-users cannot learn new spells from scrolls or spell books that they obtain, as is the case in AD&D.

At my group's OSE table, however, we've adopted the Advanced Rules for this part of the game, and have rejected the common idea that magic-users obtain a new spell upon advancing a level. As such, I've hammered out some rules of thumb for spell acquisition with the player running the magic-user .

Returning to the Classic Rules for a moment, we know that researching a new spell costs 1000 gp per spell level (taking 2 weeks per spell level), whereas recreating a lost spell book requires that each spell be rewritten at the cost of 1000 gp per spell level (taking 1 week per spell level).

Presumably the costs involve materials for special inks, paper, experimental materials or whatever, and the rewritten spell book is drawn from the magic-user's own vague memory (since no mentor is mentioned). Given the following rules additions we came up with, I think I'd half the cost of recreating each spell in a lost spell book to 500 gp per spell level.

We have decided that spells in the advanced game should be obtained either from new found scrolls or spell books utilizing Read Magic at the cost of 250 gp per spell level (taking 2 days per spell level), or from a willing mentor at the cost of approximately 500-1000 gp per spell level (taking 1 day per spell level).

After sketching out our initial ideas, I referred to Basic Fantasy RPG (which aligned with our thinking on several points), and then fine tuned some of the ideas relating to the time taken, in particular. The relevant section ("Acquisition of Spells") can be found in the BFRPG SRD here:

https://www.basicfantasy.org/srd/#dealing_with_players

Naturally, we intend to use the rules outlined above for all "arcane" spell casters where possible.

Once more, I'd like to emphasize the importance of time keeping in old-school games - it isn't cosmetic and should have in-game consequences on the game world.

Finally, we decided on some extra rules based on the percentage chance to learn spells as provided in the Advanced Rules genre book, which states that a magic-user learning a spell from a scroll or spell book must roll equal to or under their "learn spell", and if they fail they are unable to master the spell (the time and money are wasted). Rules as written, the character can never attempt to learn that spell again, but I think that's unnecessarily harsh. Instead, I will allow further attempts to be made each time the character advances a level of experience.

When learning from a mentor, however, there is the added advantage of instruction from a master of that spell, so I intend to rule that the mentor's level x2 is added to the learn spell roll, but a roll of 95-100 always indicates failure to master the spell. Note that, since I also use the half-elf class, I intend to count the mentor's level as one level lower since half-elves first gain the ability to cast spells at level 2.

While I won't provide details here, I feel that reaction rolls, availability and "role-playing/story" should also be taken into account when searching for a suitable mentor.

Well, I think that covers most of my group's current concerns on arcane spell acquisition for the time being, and hopefully the chart below helps to clarify the reasoning given above. Naturally, the costs in time and gold pieces can be adjusted as required.

	Time per level	Cost (GP) per level	Learn spell %
Learn spell from mentor	1 day	Approx. 500-1000	Base + mentor’s level ×2
Learn spell from spell book / scroll	2 days	250	Base
Rewrite known spell that has been lost	1 week	500	N/A
Research new spell	2 weeks	1000	N/A