I really like Courtney Campbell's take on the 2d6 casting check and am going to try adapting (ahem, stealing) it. The basic idea is that the caster has a pool of d6's which can be drawn from for any casting check. Allocating more dice makes a spell more likely to be successfully cast, but also more likely to bring consequences. Dice are lost from the casting pool is if the die face is equal to or lower than the level of spell being cast. Really elegant. However given I'm wanting to use this for Wonder & Wickedness spells which are level-less, that ain't going to work so well. I could just allocate an arbitrary number (say 3+) which results in a die being lost, but that's pretty boring. Another idea would be to link the number a die is lost on to the speed of spellcasting - the caster chooses a bonus to their initiative roll from 1 - 6 which then determines the roll that a casting die is lost on. That's not too bad, but its not really the flavour I'm looking for. Another element in Courtney's system is that rolls of doubles, snake eyes and box cars trigger extra results. This seems much better appropriated for how casting dice might be lost...
OK, here goes:
The base casting pool is 2d6 for anyone attempting to cast a spell. You add dice (d6's) equal to your caster level and Intelligence bonus to the pool. Dice are lost from the casting pool whilst armour is worn (1 die for each point of AC from armour/shield - I was tempted to retain armour as a penalty to rolls but its easier to go with dice all the way).
When casting a spell the caster chooses how many dice from their pool to allocate to the attempt, rolls and then consults the chart...
...however the initial rolled casting check is not the end of the story, the natural dice rolls also effects the check result and what can happen during spell casting. Whenever multiple dice come up the same number (doubles, three of kind, etc) it indicates a Spell Surge, an uncontrolled release of additional power. To contain the surge of magic the caster is forced to expend some of their power, with the result that the dice that rolled multiples are lost from the caster's pool (and are not applied to the current casting check). Multiples of "1" or "6" create additional effects:
"1" : Wild Surge - as Spell Surge, and a Spell Catastrophe occurs in addition to the results of the casting check
"6": Backlash - any 6's are removed from the casting check (but not the caster's pool) and replaced by an equal number of Spellburn dice (see below) influencing the casting check result and incurring hit point damage
Casting check result:
Favourable and unfavourable casting conditions
If the conditions for casting are particularly favourable or unfavourable they DM may rule that the caster has advantage or disadvantage on one or more casting dice. For each instance of advantage the caster may roll an additional d6 and drop their lowest (or least preferred, read: multiple) roll from their casting check. For each instance of disadvantage the caster rolls an additional d6 and drops their highest roll for their casting check (however if this would result in a multiple result being discarded drop the next highest roll). Multiple instances of each may be accrued, however any advantage and disadvantage dice cancel each other out 1 for 1 before rolling.
- Caster is in a calm environment, has surplus time and can read from their spell book (all three needed to gain one instance of advantage)
- Caster has access to special material components, a special casting location or a special casting time
- One shot magic items which are expended to boost casting attempts
- The caster may sacrifice their vitality in the form of Spellburn. Any number of advantage dice from Spellburn may be taken, however the caster also incurs hit point damage equal to the rolls (different coloured dice would be useful here).
- Caster has been damaged (not including Spellburn) or significantly interrupted during casting (one disadvantage die per time this occurs during the casting attempt - watch out for the Incomplete castig check result when surrounded!)
- Caster has lost spell from memory but wishes to attempt casting it again (this may not be a significant enough penalty - perhaps disadvantage dice accumulate each time this happens?)
- Caster is attempting to cast a spell they do not know but have access to from a spell book
- An alternative approach for balancing armour would be to incur disadvantage dice per point of AC from worn armour/shield whilst casting in armour.
In some circumstances the caster may lose control of their spell and rolls on the Spell Catastrophe table (in Wonder & Wickedness) for the matching spell school. Spell catastrophes occurs when:
- Casting check result is Miscast
- Multiple 1's rolled in the casting check
- Casters hit points are reduced to 0 whilst casting (including if damage is due to Spellburn)
|When looking for images of spell failures I googled "magic mishaps" which turned up a bunch of odd comics, involving disappearing clothes and gigantic asses/boobs/stomaches|
How are dice regained?
A night's rest if you are feeling nice, otherwise you might require some form of recharge mechanic (spend a hit dice a la 5E, consume various expensive/disgusting/illegal material components)
A few observations
- The highest possible check result is 21 (1, 2, 3, 4, 5, & 6).
- If you allocate more than 6 dice you will unavoidably get (at least) one doubles result. That doesn't mean it shouldn't be done, but the incremental value of each extra casting die decreases.
- Favourable/unfavourable conditions are the quiet achievers/killers of this system. Adjusting the incidence of multiples occurring in a casting check makes a significant impact.
- If you haven't got any favourable conditions up your sleeve and can spare a few hit points Spellburn is a good option.
- If you are going to throw a wholeloadadice at a casting check make sure you've got a bunch of favourable conditions to offset rolls of multiples. Just eyeballing I reckon you'd want at least one advantage die per four casting pool dice.
- Favourable and unfavourable conditions work well for modelling non casters attempting to use magic. They would only have access to the base 2d6 pool (+Int bonus if being generous) and would apply unfavourable conditions x2 as spell is not known or currently prepared. Other penalties for being a non caster could be applied here. However if they can add enough favourable conditions to the check they my be able to cancel these out or even reach a fairly good chance of successfully casting.
Emergent from these is that PC Magic Users will want to maximise ways of getting favourable conditions, especially through special material components or one-shot magic items. This provides lots of opportunities for Magic Users to spend their loot and for adventure hooks to chase down components and items. There could also be magic items that grant permanent favourable conditions, however this would probably be best restricted to a school of spells or even an individual spell. Otherworldly patrons might also grant favourable conditions - whilst you are in their favour of course... Magical components might also drive events in the campagin setting, e.g. a war between powerful ruling spellcasters for access to special resources (kinda like the Heroes of Might & Magic games), or a black market in certain body parts as components.
If you're interested in casting checks I'll give a shout out to Sycarion Diversions where there's been a series of posts recently exploring some similar ideas