foolofsound
2013-03-30, 11:19 AM
I doubt many people have heard of the Thieves' World series, much less played it's d20 adaptation, but I'd like to discuss one of the game's main changes to the d20 system: its spellcasting. An overview:
First, spells/day and preparing spells are out the window. Instead, all casters unlock new spell levels at the same level a sorcerer does. Casters get 2-3 Known spells per spell level (with all level 0 spells automatically known), which they can cast quickly, and 3-4 Familiar spells per level, which are cast more slowly. They may also cast Unknown spells, provided they have a scroll or spellbook to read from, though this is even slower.
Each spellcasting class has a base Spellcasting and Ritualcasting modifier. On a full caster this has 1/1 growth in one modifier and 1/2 growth in the other, or 3/4 growth in both. On a partial caster, this has a 1/2 or 3/4s growth in only one modifier. This modifier is added to the caster's primary stat bonus, and may be further modified with special magic items called foci, which give a +1-10 bonus to one of the modifiers, and cost the sames as a magic weapon of the same total bonus. This total is the caster's total Spellcasting or Ritualcasting modifier.
Let's discuss regular spellcasting first: when a caster wishes to cast a spell, he adds 1 to the spells level (modified by metamagic), then multiplies by 10 (for a total of 10-100). This is the Mana Threshold. The caster then rolls 1d20+Spellcasting modifier, and compares the result to the Mana Threshold. If the result equals or exceeds the threshold, the spell is cast at the end of the spells casting time. If the total is lower than the the Mana Threshold, the caster may either abandon the spell, or retain the result, wait another full casting time, then roll again, adding the totals, until the spell is cast. In either case, the caster takes the spells level in nonlethal damage after every cast (nonlethal damage cannot be healed through magic in Thieves' World, and magical healing instead converts lethal damage to nonlethal).
On a natural 1-5 on the spellcasting roll, no mana is added to the total, and the total is instead decreased by the unmodified d20 roll (so 1-5). If this would bring the mana total below 0, the spell backfires in some random but generally only mildly harmful way. On a natural 19-20 on the spellcasting roll, the caster may immediately roll again and add the result to the total. Interrupting a spell successfully halves the current mana total, rounding down. If the spell is already at a mana total of 0, it backfires. Casters may choose to take bonuses to their spellcasting roll at the expense of increasing the failure range, or take penalties to the roll in order to decrease the failure range.
In general, this means that most spells have a casting time of about 2-3 rounds. However, this only applies for Known spells; Familiar spells requires additional an 'preparation time' of 1 standard action per spell level OR 1 full-round action per 2 spell levels, and Unknown spells require 2 full round actions per spell level. No mana is generated during this time, and successful interruptions during the prep time ruin the spell.
Ritual casting increases the casting time of the spells to 1 minute/roll or the spell's base casting time/roll, whichever is greater. In return, multiple casters may participate in the spell, and the spells duration is increased one stage along the following: rounds/level->minutes/level->10 minutes/level->hours/level->days/level. Spells with day/level durations are not increased. Spells with flat duration increase one stage as well.
Quicken spells works differently, allowing you to cast a limited number of spells per day as a swift action so long as you can achieve their Mana threshold in a single roll. Persistent Spell does not exist.
As a side note: Thieves' World has a much greater emphasis on fighting human enemies with class levels, rather than monsters. Fights are likely to take place in tight quarters, with lots of potential cover, and the setting both expands increases the importance of social and stealth skills.
Edit: A note on charged items: staves and wands add their spells the the caster's Known list so long as they are wielded. They cannot otherwise hold charges, and spells are cast exactly as they are normally.
Points for discussion:
1: Would the increased casting time and potential for backfire, along with an in-setting doctrine of targeting casters first reduce the power discrepancy between casters and non-casters? If so, how much? If not, why? Remember that mages, in general, are likely to have somewhat more casts per day than they would in base DnD, particularly if there is significant time between encounters.
2: Is ritual casting likely to be problematic, since it can dramatically extend the durations of buff spells? Remember that Thieves' World mostly takes place in an urban environment in which magic is distrusted, so flashy buffs are likely to get you into trouble, but less obvious ones are not an issue.
3: Are the increased casting times likely to lead to casters crafting or buying large numbers of scrolls in order to avoid the issue? Will they be able to do so in such numbers that it allows them to avoid casting times altogether?
First, spells/day and preparing spells are out the window. Instead, all casters unlock new spell levels at the same level a sorcerer does. Casters get 2-3 Known spells per spell level (with all level 0 spells automatically known), which they can cast quickly, and 3-4 Familiar spells per level, which are cast more slowly. They may also cast Unknown spells, provided they have a scroll or spellbook to read from, though this is even slower.
Each spellcasting class has a base Spellcasting and Ritualcasting modifier. On a full caster this has 1/1 growth in one modifier and 1/2 growth in the other, or 3/4 growth in both. On a partial caster, this has a 1/2 or 3/4s growth in only one modifier. This modifier is added to the caster's primary stat bonus, and may be further modified with special magic items called foci, which give a +1-10 bonus to one of the modifiers, and cost the sames as a magic weapon of the same total bonus. This total is the caster's total Spellcasting or Ritualcasting modifier.
Let's discuss regular spellcasting first: when a caster wishes to cast a spell, he adds 1 to the spells level (modified by metamagic), then multiplies by 10 (for a total of 10-100). This is the Mana Threshold. The caster then rolls 1d20+Spellcasting modifier, and compares the result to the Mana Threshold. If the result equals or exceeds the threshold, the spell is cast at the end of the spells casting time. If the total is lower than the the Mana Threshold, the caster may either abandon the spell, or retain the result, wait another full casting time, then roll again, adding the totals, until the spell is cast. In either case, the caster takes the spells level in nonlethal damage after every cast (nonlethal damage cannot be healed through magic in Thieves' World, and magical healing instead converts lethal damage to nonlethal).
On a natural 1-5 on the spellcasting roll, no mana is added to the total, and the total is instead decreased by the unmodified d20 roll (so 1-5). If this would bring the mana total below 0, the spell backfires in some random but generally only mildly harmful way. On a natural 19-20 on the spellcasting roll, the caster may immediately roll again and add the result to the total. Interrupting a spell successfully halves the current mana total, rounding down. If the spell is already at a mana total of 0, it backfires. Casters may choose to take bonuses to their spellcasting roll at the expense of increasing the failure range, or take penalties to the roll in order to decrease the failure range.
In general, this means that most spells have a casting time of about 2-3 rounds. However, this only applies for Known spells; Familiar spells requires additional an 'preparation time' of 1 standard action per spell level OR 1 full-round action per 2 spell levels, and Unknown spells require 2 full round actions per spell level. No mana is generated during this time, and successful interruptions during the prep time ruin the spell.
Ritual casting increases the casting time of the spells to 1 minute/roll or the spell's base casting time/roll, whichever is greater. In return, multiple casters may participate in the spell, and the spells duration is increased one stage along the following: rounds/level->minutes/level->10 minutes/level->hours/level->days/level. Spells with day/level durations are not increased. Spells with flat duration increase one stage as well.
Quicken spells works differently, allowing you to cast a limited number of spells per day as a swift action so long as you can achieve their Mana threshold in a single roll. Persistent Spell does not exist.
As a side note: Thieves' World has a much greater emphasis on fighting human enemies with class levels, rather than monsters. Fights are likely to take place in tight quarters, with lots of potential cover, and the setting both expands increases the importance of social and stealth skills.
Edit: A note on charged items: staves and wands add their spells the the caster's Known list so long as they are wielded. They cannot otherwise hold charges, and spells are cast exactly as they are normally.
Points for discussion:
1: Would the increased casting time and potential for backfire, along with an in-setting doctrine of targeting casters first reduce the power discrepancy between casters and non-casters? If so, how much? If not, why? Remember that mages, in general, are likely to have somewhat more casts per day than they would in base DnD, particularly if there is significant time between encounters.
2: Is ritual casting likely to be problematic, since it can dramatically extend the durations of buff spells? Remember that Thieves' World mostly takes place in an urban environment in which magic is distrusted, so flashy buffs are likely to get you into trouble, but less obvious ones are not an issue.
3: Are the increased casting times likely to lead to casters crafting or buying large numbers of scrolls in order to avoid the issue? Will they be able to do so in such numbers that it allows them to avoid casting times altogether?