[RPG] Using downtime activity to research spells

dnd-5edowntimehouse-rulesspellswizard

I run a D&D 5E campaign. I have a player who is playing a wizard. This player would like to use his downtime to learn new spells. Specifically, he doesn't want to create any new spells of his own, he wants to use his downtime to write additional spells (from the PHB) into his spell-book. The PHB and DMG do not provide rules for how to handle this.

This player is both a self-professed rules-lawyer and self-professed optimizer; he is also the only one of each in the entire group. Because of this, it is very important to have a set of rules that are clear and unambiguous, but don't set his wizard up to being over-powered compared to his party-mates.

How do I allow my player's character to spend his downtime learning new spells without allowing the character to become overpowered?

A good answer will provide a set of rules or guidelines that allow my wizard player to spend his downtime adding new spells to his spell book. The rules must:

  • be clear and unambiguous
  • balance time and cost in a way that keeps this downtime activity in line with other downtime activities
    • This means that the rules should not be so constraining that spending downtime in this way feels useless, but doesn't allow the wizard to become over-powered by having access to too many spells.
  • have been used and put in-practice (in a 5E game), and the accompanying experience using the rules should be included
    • I'm not looking for, "I think you could do it this way"; I need, "We did it this way, and here's how it worked for us".

The very best answer will do the above while making it clear how this will not unbalance the party (Cleric, Ranger, Rogue, Monk, Warlock).

Best Answer

I wanted to all an alternative from all the other types of posts I see (which more or less assume this is possible). That being said this is more my interpretation of how the rules are supposed to be viewed.

The rules for how you gain new spells as a wizard are fairly clear - you gain them as you level, based on your spell book. Now that being said, it is my assumption that a Wizard is already using his downtime to learn new spells, update his notes, and in general improve his spells. My example to support this is that a fighter doesn't just go to town, sit down and drink/sleep all night (well fair point, some probably do). But most are probably training, practicing their weapon skills, or improving themselves.

I would say the rules for Wizards also support this...

The spells the you add to your spell book as you gain levels reflect the arcane research you conduct on your own

Since if you are not doing this research in your down time, when are you doing it?

Aside: Now, it would be a separate issue if say the Wizard found a spell book, or notes about some spells he did not already know. But this strikes me as more of the role-playing side, and I don't intend to cover that in my answer.

If you decide to allow it, I would highly recommend making it massively less useful for your Wizard. A good method would be to use the spell copying table mentioned in other answers and use that as the time required (I expect this would dissuade him from trying anything other then the lowest level spells). It seems the rules outlined for this (both time and money) are fairly penalizing - I might also add a failure chance for a bit of home-brew flavor as well (e.g. the Wizard was attempting to write a spell he did not already know and did not gain through practical use).