Spell Failure in Blackmoor

Magic in early Blackmoor has often attracted interest, in part because it appears to have been so different from the "Vancian" system Gygax adopted for D&D.  When Arneson developed the magical component of his Blackmoor campaign he had little to go on in terms of source material.  The first edition CHAINMAIL booklet did list a handful of battlefield spells, but not much else.

In his write up in the FFC titled "Original Blackmoor Magic", Arenson supplies a good general description of the methods he devised, but few of the specific details the curious gamer might wish for.  However, by pulling in information from other Blackmoor sources, we can cobble together a more complete picture.

In particular, one aspect that has drawn some attention and has attracted a number of fans over the years is the idea of spell failure.

Arneson wrote: "...there was always a chance of failure in spells (unless they were practiced)"  FFC77:74

Presumably "they" means the spells, though it could mean the wizard, which might be more sensible, since it is unlikely Arneson or anyone else would want to keep track of how many times a wizard cast a particular spell in order to maintain some threshold of being "practiced" with it.  Given that Arneson also tells us "...to progress to a new level, one first learned the spells... there was no automatic progression, rather it was a slow step by step, spell by spell progression." FFC77:74, we can read that to mean mastering a spell level to the point of no failure meant you were "practiced" with those spells.

We know from other sources - the Corner of the Table Newsletter in particular - that wizards also had "levels".  The highest level we know of being 12, in the case of a 12th level sorceress mentioned in the after action report of the July 1972 battle of Lake Gloomin.

We also know that spell failure varied among casters.  The description of the Gin of Salik tells us "His magic spells are among the most potent in the world with no chance of them failing..." FFC77:20

For the 7th level Ran of Ah Foo: "He also has a spell workshop that turns out one Level I spell a week and one Level II spell a month with one level III spell a year.  These are portable but not reusable with only a 15% failure rate."  FFC77:19

And finally, the bumbling Egg of Coot, who sells spells with a "30% chance of failure per level of spell, i.e. III = 50%, II = 40%, etc."  FFC77:18

A last bit of information to consider is the number of spell levels themselves.  The highest spell level appears to be level IV, because of the Gin's spells we are told. "All of which are level IV, at a rate of one every two months..." FFC77:20

Thus we have some numbers to play around with here.  Correlation does not equal causation, but the above certainly suggest, as we might expect, that as a wizard advanced in level their rate of failure declined, so let's go with that and see where it leads.  We can start with the Egg and assume he (or whoever makes his spells) is a Wizard of unknown level producing spells of levels I through IV.

The failure pattern at this level x is:

Spell level I,  30%
Spell level II  40%
Spell level III 50%
Spell level IV 60%

If the Ran is really level 7 and has a 15% fail rate, the the pattern above would seem to change in 5% increments.  The text implies all of his spells fail at 15%, so perhaps there is a change of the rules between these two examples, but if we presume this rate applies to Ran's best spells (level 3), we get this:  

Spell level I,  5%
Spell level II  10%
Spell level III 15%
Spell level IV 20%

However, if we go back to the Eggs failure rate, and improve in 5% increments from the worst it could represent (1st level wizard), we get a table like this:

Wizard Level	I Spell	II Spell	III Spell	IV Spell
1	30	40	50	60
2	25	35	45	55
3	20	30	40	50
4	15	25	35	45
5		20	30	40
6		15	25	35
7			20	30
8			15	25
9				20
10				15
11				10
12				5

We're told the Ran is 7th level but the 5% table based on the Egg's failure rate tells us that a 7th level wizard should have a 20% failure rate at level 7 and a 15% failure rate at level 8.  So either the Ran is 5% better than he should be, or the Egg is 5% worse.  

Interestingly, we are told the Egg has a mere "level II intelligence with a mature age of 3 to 6." FFC77 p18  Ascribing a 5% penalty for low Intelligence may seem too "modern" an idea, but it isn't outside the realm of possibility of what Arneson might have done.   
In any case, it works for us, so let's recast the table assuming Ran has a "standard" failure rate.

Wizard Level	I Spell	II Spell	III Spell	IV Spell
1	25	35	45	55
2	20	30	40	50
3	15	25	35	45
4	10	20	30	40
5	5	15	25	35
6	0	10	20	30
7	0	5	15	25
8	0	0	10	20
9	0	0	5	15
10	0	0	0	10
11	0	0	0	5
12	0	0	0	0

There's a couple more reasons to prefer this second table, first, because it benefits players slightly, and secondly because it zero's out at level 12, which is the highest level we know of as mentioned earlier, and we know in at least the case of the Gin of Salik, it is possible to be at a level so high your spells do not fail.

To apply this table to D&D spells, the Referee should change only the range of spell level, and I would recommend that only for the last 2 columns so that "III spell" becomes Spell level 3 &4, and IV Spell becomes spell levels 5 & 6.

What exactly happens when a spell fails is up to you.