Homebrew Magic System



I’ve been thinking up a way to do magic, I enjoy the old school Vancian casting rules but I find most new players are resistant to the idea of spells requiring components and tracking different levels of spell slots. Here’s what I’ve got so far

Magic - Casting a spell requires an ability check of the ability score tied to the spell type (Intelligence for Arcane)

The target for the check is determined by the spells level

Level 1: 14

Level 2: 16

Level 3: 18

Level 4: 20

Spells are typically not depleted upon use and do not require material components to cast, the trade off being that they are not guaranteed to be cast since they require a check.

Equipment can reduce the target of casting certain spells/ Increase ability scores used for casting. I would avoid making equipment that lowers the requirement across the board for all/many spells and instead create items that make specific spells easier/guaranteed.

Powerful spells should be difficult to obtain, perhaps requiring specific materials to research, or a quest or npc involved in obtaining them. Examples: Perform a ritual to summon a demon to teach you fireball or some other destructive/ hellish spell, surviving a lightning strike to learn lightning bolt.

Ritual Casting - Some spells can be cast as rituals.

They do not require a check, instead the spell will have hearts of effort equal to the level of the spell. (A level 2 spell has 2 hearts and so on)

If the ritual is interrupted the caster must start over.

Other magic users can help perform the ritual.

Let me know what you think, this is my day one draft of these rules so they are bound to change.


Nice. I like it. For my homebrew system, I use the following (in case this gives you some idea’s)… You can cast on your turn any spells you have memorized (chosen in the morning each day). Memorized spells is equal to your Intelligence stat. ie: 5 = 5 memorized spells. If you cast a non-memorized spell… you skip this turn and cast first in the lineup on the next round (unless you are interrupted during this round). All spell castings cost 3 mana. Mana is equal to Intelligence x 3. ie: 5 Int = 15 mana. Once mana is depleted, you can cast using HP’s for the same cost. You roll a d20 when you cast but only to see if a 1 comes up. Otherwise, you cast no problem. To boost your range, duration or damage, you simply add mana (or HP if out of mana) to it. For example, magic damage is d10, you roll a 3 but this is a critical battle so you want to throw everything you got at the bad guy and spend all 15 of your mana points. The damage is now 15+3 for 18 damage. This gives the magic user the opportunity to be a tank as well if they so choose. Range… 1 mana spent boosts it for 1 more yard. Duration, 1 mana spent boosts it for another round. To me, magic users are always so heavily restricted that they don’t have as much fun as the fighters do. I think this system allows the magic user to have that fun. They can cast without fear (other than a dreaded 1 showing up) but that fun only lasts as long as they have mana so it is limited. They can cast and do epic damage but again… that is also restricted by the mana level. Should they opt to use their life essence (HP’s) to power up their spells… that’s on them. A mage can in effect… die a hero if they use all their mana and hp to power up the damage on a casting. Imagine a spell that does 1d10 + all mana of say 21 and all but 1 hp of say… 35 total for a one time damage of max 56 points!! That could be half a dragon, a horde of goblins, a small contingent of Orc’s, etc.



This seems like a very workable system, and while I prefer the unity of the ICRPG room target and don’t personally enjoy “spell levels”, those are simply matters of taste. I’d note that few of the spells in ICRPG have the big payoff to make ritual casting worthwhile in the midst of danger, and without that danger, the hearts of effort are going to feel perfunctory. That said, if you are able to write some cool spells which players would be tempted to cast as rituals, that could be an exciting moment. On the other hand, more than 2 hearts is going to feel like it’s taking forever at the table. Let us know how it plays, and report back on your tweaks.


I’m not planning to use many icrpg spells. I’m mostly using spells and monsters from the b/x books, I’m trying to mash up the simple systems I like from icrpg and combine it with what I like about older dungeons and dragons to make a system that’s perfect for the kind of game I want to run.
Most of the content from Alfheim doesn’t appeal to me, besides some of the loot. Nothing against that setting its just not for me.


I don’t get a lot of gas in the can from Alfheim as a setting either; used a bunch of the base ICRPG spells as inspiration for what I thought of as “more magical” spells. Was old B/X just a 4 level spell list, or did it go up to 9?


I think it goes up to 9 so I’m not sure what I’m going to do about that yet. I’ll probably have to expand the levels in the system while crunching some of the spells into fewer tiers. To clarify “B/X” is the former name of a product that’s now called “old school essentials” by necrotic gnome. It’s a revised version of basic and advanced dungeons and dragons. It’s a great resource, I highly recommend it.


For someone who’s not into “leveled” play anymore, what’s the best part of it as a resource?


If you’re not into leveled play, then it’s not really something I would recommend you pick up.

For leveled play, it’s a pure distillation of the essence of Dungeons and Dragons, and in a lot of opinions, the best version ever created.

What I love about 70s - 80s DnD these days is how modular everything is. Sure, d20 roll high against a DC or Target is great, but once you tie everything to that mechanic, any hacking you do has to follow those same guidelines. With OSE(B/X) you have multiple mechanical systems, and you can pull one out and replace it very easily without much work on your side. This is most definitely why it’s the base for so many OSR systems, it is just so damn easy to work with.

For me, it’s fantastic as a base. But I recently picked up Hyperborea 3e, and the base rules in that system are somewhere between B/X and 1e, but very well organized, and cleaned up. It’s quickly becoming my favorite version of “DnD” to date.


I think you could get a lot of use out of the monsters book. Stat wise they fit right in in ICRPG, their health ranges from around 10 for weaker enemies to around 50 for really big dangerous monsters. Most monsters have a standard attack and some sort of special ability: a giant frog can swallow small characters, a frost salamander radiates cold damage, undead can steal xp from PCs.
Besides that there are notes for monsters that really get you thinking about what you could do with them in your campaign. For instance frost salamanders will attack flame salamanders on sight, I’m prepping a campaign set in a frozen wasteland with a frost salamander as one of the prominent monsters, and now I’m thinking “where could I have a flame salamander that the players could possibly pit against this thing?”
The section on dragons is especially nice, there’s all kinds of things like the likelihood of a dragon being capable of speech, or how much they are worth if you can capture one.


Might a Flame salamander be near a volcano or Hot springs? Those can be part of a northern wasteland territory.