Stressed Spell Casting

I am working on houserules for my Astonishing Swordsmen and Sorcerors of Hyperborea campaign this morning. The main topic of the moment is variation from straight old school Vancian magic. Back in my 80s OD&D campaign I addressed making magic less predictable and a bit more epic, by including a D20 roll at every spell cast to get a spell off, with fumble and crit effects, spell level, caster level, and casting attribute bonuses involved, and allowed overcasting beyond spell slots at a penalty to the roll and taking HP damage based on the level of the spell and how the roll went. So casting was pretty reliable until spell slots were used up, then less so, and costing damage to self to overstrain. It worked pretty well, but was not really high on story flavor.

The primary concept is that magic is chimerical and capricious. A sorceror can manage the inherent riskiness of magic by preparation and not overtaxing himself. Vancian "finals cramming, with memory wipeout" style has always seemed odd to me, especially with multiple copies of the same spell being memorized into slots. So I will use each spell slot two ways. It is a spell that the sorceror has prepared enough that day to be as safe as possible and a packet in a sorcerous energy buffer to allow spells to be cast without undue strain. So a caster has two first and one second level slots can have two first and one second level spells prepared, and could cast either first level spell with each first level slot and either one or the prepared second level spell with the second level slot. That's all pretty straightforward and pretty similar to a 3rd Ed or 5th Ed sorcerer.

Various circumstances will add STRESS to a spell casting, and with Stress things are more likely to go wrong and in unpredictable ways. Stress will be a sort of currency, casting a spell with more Stress will likely make it go more spectacularly wrong. Casting with even one level of Stress should be dangerous. More should be really scary. Casting a spell over your level is a deeply desperate measure. This mechanic might replace various printed mechanics relating to armor, scrolls, interruption by damage, etc.

Stress causes I am considering using:

Cause of Stress	Amount of Stress
Not having the spell prepared	1 (2 if spell level > 3 )
Not having the spell slot for it	spell level/2
Cast a spell from your list and level range that you have seen but do not have in your book/preparable repertoire	2
Each armor step beyond sorcerer's Armor Allowed	1
Being struck for damage during the cast and not aborting	1
Casting anything besides touch attack/melee escape spells in melee contact	1
Cast a spell over your highest spell slot level	2 + 2/level over
Ritual casting - extended time and materials	-1
Using a scroll from outside of your school, for a spell shared by your school	1
Using a scroll from outside of your school, for a spell not shared by your school	2
Casting using a scroll beyond your level	1+

Each point of Stress will cause one roll on the table below. For each result, I plan to offer the choice of the rolled result and the next one farther down in the list. Followup rolls will be AFTER the choice. Each point after the first will modify all rolls by +5. Dungeon Crawl Classics has some nice tables in the right direction, so some of these results refer to those tables, which might take some results reinterpretation to fit in.

Roll	Effect
01-20	Escaped without harm
21-30	Spell fizzles
31-35	Add a level of Stress to all casting until well rested
36-40	Wipe out preparation of one spell (the attempted one first, if prepared).
41-45	Wipe out energy of one spell slot(the attempted one first, if slot was used, else highest available).
46-49	Knocked down
46-49	Destruction of minor or consumable magic item on caster (1st) or friend
52-55	Attract the unwanted attention of a nearby magically sensitive creature
56-58	knocked back 10 feet per level of spell
59-61	Destruction of an item in hand
62-64	Stunned for one round
65-67	DCC Generic Spell Misfire (5-6, pg 120)
68-70	Attract the unwanted attention of all nearby magically sensitive creatures
71-73	Save vs or Stunned for one turn
74-76	Experience point loss - 1D4 x 5% of highest level
77-79	DCC Minor Corruption (5-3, pg 116)
80-82	Take 1D6 psychic damage per level of spell
83-84	Attract the unwanted attention of a powerful but potentially remote magically sensitive being
85-86	Roll on the madness table, effect lasts 1D6 days
87-89	Take 1D6 damage to a random attribute
91-94	DCC Major Corruption (5-4, pg 118) if arcane or Deity Disapproval 5-7 if divine (chaotic or evil divine could be either)
95-97	Destruction of a significant magic item on caster or friend
98-100	The spell gains/replaces a Mercurial Magic effect (DCC 5-2, pg 111)
101-102	Gate in an inimical demon of level equal or up to 2 higher than caster, within 30' of the caster
103-105	Destruction of a most significant magic item on caster or friend within 30 feet
106-109	DCC Greater Corruption (5-5, pg 119) arcane; deity disapproval, worse of two rolls, if L/G/N divine; C/E divine could be either
110+	Attract the (potentially ongoing) attention of an inimical divine being. In this campaign that might mean Cthulhu awakens, and starts disturbing the caster's dreams, sending minions, and eventually showing up itself.

So, Bilzor the Magician, at first level, has cast his one prepared sleep spell for the day, and his party is being overrun by bandits. He tries to save the day by casting another sleep spell, but his only spell slot is drained. He rolls a 47 and has the choice of loss of a minor magic item or attracting the attention of a nearby magically sensitive creature. He picks the item, and since he has a Potion of healing and a level 1 spell scroll, the GM dices and the potion bottle shatters. Had he picked the attention, he gets a creepy being watched feeling, and the DM consults his notes and decides the Ixian witch a level deeper in the dungeon feels the emanations of the reckless spell, and gets a glimspe of Bilzor in her mind's eye, and a general sense of where he is, and might come hunting for him or is at least alerted, can make preparations, like dispatching a minion to spy, and is not surprised by the party for the next day.

Later in the fight, the party's fighter goes down, Bilzor is beset by a pair of bandits, casts a further sleep spell, and is struck by one of them before he gets it off. This time, he'll have 3 Stress, for overcasting beyond his slots, melee, and being injured while casting, and will be adding 10 to each of three rolls. With a 16 first roll that would have succeeded without backfire in the first instance, he now has a 26 result, and the sleep spell fizzles or he has additional Stress for any further casts until he can rest for the day. He chooses the Stress so his spell might go off. The second stress roll of 77 becomes 87 and he declines the permanence of DCC major corruption and takes a 3 point hit to his CHA after followup rolls, the DM decides these points will recover at one per week. The third roll of 52 becomes 62 and he is stunned for a round, declining the DCC misfire table. Bilzor might survive to recover that CHA if the spell puts all his enemies to sleep.

I'll probably tweak this some more, but it gets pretty close to what I want in letting low level casters not be one trick ponies, but with significant risks, and letting higher level casters get themselves into deep trouble when they attempt great feats of magic.