Paring Down 5th Edition #2: Simplifying Spell Points, and a Dice-Based Variant

tl;dr:

idea 1: spells cost MP/mana/spell points equal to their spell level. This ends up being surprisingly close to the DMG costings.
idea 2: instead of having fixed MP/day, casters have spell dice/day. For each MP needed, casters roll a magic die (a d6). A natural 1 or 2 means the die is expended for the day. Different conditions, caster specialisation, or defiling/preserving may change these odds. Additional mechanics for particular results (doubles, triples, runs, etc) may be invented as desired.
See the Longwinded Explanation (after the cut) for reasoning and advice on which column to choose. Sorry for the lack of CSS.

Table 1: MP and Spell Dice by Level (with and without Arcane Recovery)

Level	MP	MP (+AR)	Spell Dice*	Spell Dice** (+ AR)
1st	2	3	1	1
2nd	3	4	2	1
3nd	8	10	4	3
4th	10	12	5	4
5th	16	19	8	6
6th	19	22	10	7
7th	23	27	12	9
8th	27	31	14	10
9th	36	41	18	14
10th	41	46	21	15
11th	47	53	24	18
12th	47	53	24	18
13th	54	61	27	20
14th	54	61	27	20
15th	62	70	31	23
16th	62	70	31	23
17th	71	80	36	27
18th	76	85	38	28
19th	82	92	41	31
20th	89	99	45	33

* Dice expire on a 3 or less
** Dice expire on a 2 or less

Longwinded Explanation

I don't mind Vancian magic, but it has to be closer to strict Vancian magic, not the rather complicated version 5e presents.

While overall a *little* better than 3rd edition -- I like how multiclass characters use the same pool of spell slots for all their spellcasting classes -- there's weird fiddly extra layers: racial spell slots are tracked separately, warlock invocations grant 1/long rest spells that still use short-rest spell slots, Arcane Recovery, casting spells At Higher Levels, Sorcery Points that are fungible with spell slots but are also spent on their own things...

It's a mess. Just make casters use MP already. Now the Dungeon Master's Guide does have a spell point variant, but it doesn't interface well with Arcane Recovery or Sorcery Points, and the cost of each spell level is hard to remember.

The obvious alternatives are either:

1. Casters can spend MP equal to their character level (or caster level, if multiclassed). 1st level spells cost 1 MP, 2nd level costs 3, then 5, 7, and so on. Third edition psionics used this approach.
2. Casters can spend MP equal to their highest known spell level, and each spell costs MP equal to their spell level.

But how do these options compare to the DMG guidelines? It's pretty easy to find out, just convert the spell slots available to a vanilla 5e caster at each level (1st to 20th) into MP, using all three conversion methods ("DMG", "1357", and "1:1"). Note that doing this for "DMG" produces the exact same table as the DMG, as one would hope. Then convert the MP totals back into spell slots of each spell level, for each class level, and look at the difference between how many spell slots you can eke out with each method.

The simplest way to present this information is as two tables.

Table 2: Difference Between "1357" and "DMG" Spell Point Costs

Level	1st	2nd	3rd	4th	5th	6th	7th	8th	9th
1st	0	-1	0	0	0	0	0	0	0
2nd	0	-1	-1	-1	0	0	0	0	0
3nd	3	-1	0	-1	-1	-1	-1	-1	-1
4th	5	-1	-1	-1	-1	0	0	-1	-1
5th	10	-2	-1	-1	-1	-1	-1	-1	-1
6th	12	-1	-1	-1	-1	-1	-1	-1	-1
7th	16	-1	0	-1	-2	-1	-1	-1	0
8th	20	0	0	-1	-2	-1	-1	-2	-1
9th	30	0	0	-1	-2	-1	-1	-2	-1
10th	35	1	1	-1	-2	-1	-1	-1	-1
11th	42	2	1	-1	-2	-1	-1	-1	-1
12th	42	2	1	-1	-2	-1	-1	-1	-1
13th	50	3	2	0	-1	-1	-1	-1	-1
14th	50	3	2	0	-1	-1	-1	-1	-1
15th	59	4	3	0	-2	-1	-1	-1	-1
16th	59	4	3	0	-2	-1	-1	-1	-1
17th	70	6	3	0	-2	0	-1	-1	-1
18th	75	6	4	-1	-2	0	-1	-2	-1
19th	82	6	4	0	-2	0	-1	-2	-1
20th	90	8	5	0	-2	0	-1	-2	-1

Table 3: Difference Between "1:1" and "DMG" Spell Point Costs

Level	1st	2nd	3rd	4th	5th	6th	7th	8th	9th
1st	0	0	0	0	0	0	0	0	0
2nd	0	-1	0	-1	0	0	0	0	0
3nd	1	0	0	0	-1	0	0	0	-1
4th	2	0	0	0	0	0	0	0	0
5th	3	-1	0	0	0	-1	0	0	-1
6th	3	-1	0	-1	-1	0	-1	0	0
7th	4	-1	0	-1	-1	-1	0	-1	0
8th	5	-1	1	-1	-1	0	-1	-1	0
9th	8	-1	1	0	-1	0	0	-1	0
10th	9	-1	1	0	-1	-1	-1	0	0
11th	11	-1	1	-1	-1	-1	-1	-1	0
12th	11	-1	1	-1	-1	-1	-1	-1	0
13th	13	0	2	0	-1	0	-1	-1	0
14th	13	0	2	0	-1	0	-1	-1	0
15th	15	0	2	0	-1	0	-1	-1	-1
16th	15	0	2	0	-1	0	-1	-1	-1
17th	18	0	2	0	-1	0	0	-1	-1
18th	19	0	3	0	-1	0	-1	-1	0
19th	21	0	3	0	-1	0	-1	-1	0
20th	23	0	3	0	-2	0	-1	-1	-1

So immediately we see "1357" diverges more from "DMG" than does "1:1". This is not inherently bad, but for my purposes -- making classes with a roughly equal "power level" to vanilla 5e classes -- I'm going with "1:1". 1st-level spells still diverge a fair bit, but to be honest, if a mid level caster's going to forgo their highest level spell slots to cast 9 more magic missiles than they could under DMG guidelines, I'm pretty OK with that. It's actually a kinda neat capstone of sorts for mid-to-high level play. "You can cast 1st level spells more or less at-will, within reason", is more interesting to me than some far-off Spell Mastery ability that makes a spell literally at-will, but is placed so high at 18th level that it's meaningless for the vast majority of games.

1:1 also interfaces easily with Arcane Recovery. A wizard (or Land druid) just regains MP equal to the number of spell levels their feature would give them. Or you can just include them in overall MP/day and not require the short rest, unless you're concerned about casters going nova.

Spell Dice

 Now if you just want a simpler spell point system, you can stop reading. But I want an element of risk and excitement whenever someone casts a spell, beyond the simple resource management of "if I blow my slots now, I won't have them later."

Now if I was designing from scratch, I'd probably have magic-users cast from HP (most players these days understand hp is more like stamina than # of arrows one can take to the chest), have at-will casting with a chance of mishap, or rewrite all the spells so their effects are unpredictable. But for a set of houserules for use with unaltered 5e adventure material, the act of casting a spell has to stay pretty safe and not leave someone physically drained.

So I want to play around with the idea of casters having a pool of spell dice, and an Expiry number. Whenever they cast a spell, they have to roll a number of unexpended "spell dice" (d6) equal to the spell level. Any dice whose natural result is less than or equal to the Expiry number are expended for the day (or until the next short rest, if a warlock).

Depending on how you want to handle Arcane Recovery, there's two possibilities:

1. Without Arcane Recovery, starting casters should average 2 spells/day, so they start with one spell die which expires on a 1-3.
2. With Arcane Recovery, starting casters should average 3 spells/day, so their one spell die expires on 1-2.

Option 2 has some obvious issues at 2nd level. Either you give casters their second spell die, and they can cast an average of 6 spells/day, which is pretty powerful, or it's a dead-ish level. They still get their class features and more spells known/prepared, but no extra spells/day. But still, I think an expected value of 4 spells/day (and a guarantee of 2), better fits my wishes. Not every character wants that many spells/day -- obviously Moon druids are willing to forgo their extra spells/day in favour of a better wild-shape. Extra Spell Dice can be an optional class feature or a feat.

Obviously there's other options, like an Expiry that starts high and decreases as a caster gains levels, but I don't want to resort to that just yet. Though if I were houseruling B/X this way, starting with 1 spell die at Expiry 6 would be appropriate. I also really don't want to mess around with different die types or have different-colored d6 all with their own Expiries, but perhaps you feel differently.

Now, having an Expiry number opens up some interesting mechanical space. Here are some ideas for modifying Expiry based on circumstance. Modifiers are cumulative, Expiry cannot drop below 0, and if it would rise above 6 the spell cannot be cast (or fizzles if this happens during casting).

• Specialist wizards have -1 Expiry when casting a spell from their favoured school.
• Getting hit while casting a spell adds +2 Expiry, instead of the caster making a concentration check.
• For a Dark Sun game, defiling and preserving have different Expiries. Other settings can have special locations (leylines, places where the Weave is threadbare, magical interference from a nearby wizard's tower) that raise or lower Expiry.
• Metamagic costs Expiry.
• Bargain with your deity or warlock patron to briefly lower your Expiry.
• Anyone can cast spells in armor but it's more tiring, at +1 to Expiry per armor category.
• Any spell can be cast as a ritual, for an Expiry of 1.
• Cut down on the number of "xd6 damage of some element" spells by giving all casters a default magical attack, and combining the roll for damage with the spell dice roll. To be in line with 5e expectations, this would require a couple of differently-coloured d6 that don't count as spell dice, but add to the damage of the spell.

Naturally this would require some playtesting to figure out what changes are easily understandable and are actually fun. e.g. having lots of Expiry modifiers that can be opted into in the middle of combat will slow it down, an undesirable outcome. It also runs the risk of giving casters a lot of free power, e.g. a "cast without components by raising Expiry" option would make it very difficult to neutralise a spellcaster by taking their wand, binding and gagging them.

As for whether the natural results of spell dice could be used in other ways, perhaps a rewritten wild magic table could make use of them? I'll have to think about how to structure a table in a way that doesn't care about the order of d6 results.