Last night, I ran two Words of Power spellcasters against my group, which consists of the following PCs:
LE tiefling cleric 10
LE elf rogue 5/assassin 5
CE human antipaladin 10
NE elf sorcerer 10
The casters, CR 8 constructs called darkwood magems, were allied with two CR 7 magic-immune construct warriors wielding double-bladed swords (nicknamed mithril choppers) that served to bottle neck a hallway while the casters did their work. The map I used was the main long hallway from the Hall of the Elestial Eye map in Dungeon #140 that is sandwiched by stairwells and features the tiered balconies on either side. The two construct warriors waited atop the 20'-high balconies; the pair of construct casters was positioned on the 40'-high balconies.
One thing that may have thrown off the balance on this playtest is the fact that despite the casters being constructs, I ruled them to be subject to mental ability score damage. These creatures were modeled after 3.5 warforged; thematically, they are golems endowed with intelligence and aptitude by their creators. I decided that since they were magically gifted with intelligence, the sorcerer's touch of idiocy spell could similarly take away that mental aptitude. Nonetheless, I was pleased with their performance.
Blow By Blow
Prior to combat, both casters used their dweomers of protection to boost their ACs and get temporary hp and save bonuses. The battle then began with the choppers dropping from their perches and blocking the hallway, which kept the antipaladin and cleric engaged.
One caster unleashed an acid rain spell on the three PCs in the south end of the room (the rogue was already out of the way, having opted to use Acrobatics to leap from balcony to balcony and go after the caster on the left), dealing about 35 points of damage before applicable saving throws. A single-target plasma bolt from the other caster hit the antipaladin, doing 18 points of unavoidable force damage (after reading the rules carefully, I decided that the force damage could never be halved on a successful save, even if it was combined with an elemental effect that would have been halved).
The sorcerer used spider climb and greater invisibility to reach the caster on the right unnoticed. By round two, the assassin engaged the caster on the left but realized too late that their 27 AC was going to be a bit much for him to eat through. By the end of round three, he was unconscious from the magem's caustic torrent spells.
The magem on the right didn't fare as well - in round two, he was hit with a touch of idiocy that dropped his Int to 12, meaning he couldn't use any spells higher than 2nd level. To boot, the sorcerer was still invisible, so the dumbed-down magem focused on helping his buddy pelt the rogue with his orbs of pain, then moved south to aid the choppers, dropping more orbs of pain on the antipaladin. The save DCs were reduced due to the touch of idiocy, so the non-damaging effects didn't have any effect - but boy, that force damage did. :)
Round four, sorcerer spider climbs across the hall, hangs from the ceiling, and uses touch of idiocy on the other magem. Magem retorts with a hellfire spell, but completely misses - because although he could determine the spell's general point of origin, he fired the spell at eye level, missing the sorcerer by about five feet. Meanwhile, the magem at the south end uses walk on your grave to deal cold damage to the antipaladin and cleric.
Combat ended in about seven rounds - the antipaladin and cleric dropped the choppers with melee attacks and searing light, and a channel negative energy and vampiric touch polished off the magems.
Analysis
I found the WoP spells to be pretty well balanced; word burning and effect stacking allowed me to create some unusual effects, but realistically, the level of the PCs meant most of those effects were negligible at best (the 1d3 acid damage on caustic torrent, for instance, is really just adding insult to injury over the force damage). I certainly didn't feel more or less powerful than I would have just by using spells out of core and APG, though, so in that respect WoP is okay.
The build process for the darkwood magems was excruciating, however. I spent about 45 minutes statting up the base creatures, and about 3 hours building WoP spells. I actually had to go back and redo a few because I realized after the fact that force bolt was single target only; I was so bogged down in getting word totals and requisite burn points calculated correctly that target limitations escaped my notice until I went back through for one last check over.
I think WoP adds an interesting element of spell creation to the game that's fun for casters who want to add unique flavor to their spell choices, but in practice it's time consuming and cumbersome. I'm glad I chose to build casters who prepare rather than cast spontaneously, because assembling these spells on the fly would be an invitation for slowdown at the table and mistakes that could unbalance the game due to a misconstrued rule application.
WoP is, however, a good alternative to traditional spell research in that the word costs make it easy to create something that's more or less balanced. I may try to talk my GM into letting me use WoP or a variant thereof to build a completely custom caster in the near future.
As has been discussed in other threads, I think effects like staggering and entangling that are tied with elemental effects should probably be separated and treated as extra add-on effect words so that casters don't feel limited in their choices; if I want to make an ice or acid themed caster using WoP, I don't want those increased costs to limit my ability to do so using RAW.
I may rerun this playtest tonight if I have enough time and interested players; if the results vary greatly, I'll post them as a response to this thread.
Many thanks to the designers and developers for making this available for playtesting - despite my criticisms of the system, it has been a lot of fun to dither around with!
Stat Blocks and Spell Descriptions
Here are the stats for the WoP casters I built. The individual spells built using WoP are detailed beneath their stat block.
Warmech, Darkwood Magem CR 8
XP 4,800
N Medium construct
Init +2; Senses darkvision 60', low light vision; Perception +6
DEFENSE
AC 21, T 13, FF 18 (+2 Dex, +1 dodge, +8 natural)
hp 64 (8d10+20)
Fort +3, Refl +5, Will +4
DR 5/-
Immune construct traits
OFFENSE
Speed 30'
Melee 2 slams +9 (1d6+1)
Ranged ranged touch +10 (by spell)
Effect Words in Spellbook:
0th - acid burn, cold snap, cramp, echo, flame jet, force block, sense magic, spark
1st - burning flash, force shield, fortify, servitor I, shock arc, simple order, spook, wrack
2nd - burning flash (boosted), force bolt, frost fingers, sense thoughts
3rd - complex order, fire blast, force armor, torture
4th - acid wave, ice blast, simple order (boosted), terror
Spells Prepared (CL 8)
Magem 1:
0 - cold snap, cramp, flame jet, spark
1 - cinderburst x 3, shock arc x 2
2 - caustic torrent x 2, walk on your grave x 2
3 - dweomer of protection, hellfire, plasma bolt
4 - acid rain
Magem 2:
0 - cold snap, cramp, flame jet, spark
1 - cinderburst x 3, shock arc x 2
2 - orbs of pain x 3, walk on your grave
3 - dweomer of protection, hellfire, plasma bolt
4 - breath of the silver wyrm
STATISTICS
Str 13, Dex 14, Con -, Int 16, Wis 12, Cha 10
Base Atk +8; CMB +9; CMD 21
Feats Combat Casting, Dodge, Improved Natural Attack (slam), Word Burning
Skills Knowledge (arcana) +10, Knowledge (planes) +10, Knowledge (religion) +10, Perception +7, Spellcraft +10, Use Magic Device +6
Languages Abyssal, Celestial, Common, Draconic
4th Level Words of Power
Acid Rain (acid wave 9, small burst 3)
SR No; Reflex DC 17
Range/Effect: Close (45', 10' radius burst)
8d6 acid damage for 2 rounds, and targets are sickened for 8 rounds; successful save reduces duration of sickened condition to 1 round
Breath of the Silver Wyrm (ice blast 9, medium line 3)
SR Yes; Reflex DC 17
Range/Effect: 60' line
8d6 cold damage and targets are entangled for 1d4 rounds; entangled effect ends if target takes 8 or more fire damage in subsequent rounds
3rd Level Words of Power
Plasma Bolt (fire blast 6, force bolt 8, single 0, requires 4 burn points)
SR Yes; Reflex DC 16
Range/Effect: 1 target within 45'
Target takes 8d6 fire damage and 5d4 force damage; force damage is not halved on a successful save
Hellfire (torture 6, burning flash 5, medium line 3, requires 4 burn points)
SR Yes; Fortitude DC 16
Range/Effect: 60' line
Targets are nauseated for 8 rounds (new save at end of each turn to negate) and take 5d4 fire damage
Dweomer of Protection (force armor 7, fortify 5, personal 0)
SR Yes (harmless); Will DC 16 (harmless)
Range/Effect: Caster only
Target gains a +6 armor bonus to AC for 80 minutes, and a +1 resistance bonus to all saves and 8 temporary hp for 8 rounds
2nd Level Words of Power
Walk On Your Grave (frost fingers 5, spook 4, mass 2, requires 4 burn points)
SR Yes; Reflex DC 15
Range/Effect: Medium (180', up to 8 targets within 30' of each other)
5d6 cold damage and staggered for 1 round, and targets with less than 5 HD are frightened for 1d4 rounds
Orbs of Pain (force bolt 5, wrack 4, single 0, requires 2 burn points)
SR Yes; Fortitude DC 15
Range/Effect: 1 target within 45'
5d4 force damage and target is sickened for 8 rounds; a successful save does not halve force damage
Caustic Torrent (force bolt 5, acid burn 3, single 0, requires 1 burn point)
SR Yes; Reflex DC 15
Range/Effect: 1 target within 45'
5d4 force damage and 1d3 acid damage; a successful save does not halve force damage
1st Level Words of Power
Cinderburst (burning flash 3, mass 2)
SR Yes; Reflex DC 14
Range/Effect: Medium (180', up to 8 targets within 30' of each other)
5d4 fire damage
Shock Arc (shock arc 4, single 0)
SR Yes; Reflex DC 14
Range/Effect: 1 target within 45'
5d4 electricity damage
Words of Power Cantrips (all are single target)
Acid Burn: 1d3 acid damage, 1 target w/i 45', requires ranged touch, no save
Cold Snap: 1d3 cold damage, 1 target w/i 45', requires ranged touch, no save
Cramp: base speed reduced by half for 1 round (minimum 10'), Fortitude DC 13
Flame Jet: 1d4 fire damage, 1 target w/i 45', requires ranged touch, no save
Spark: 1d4 electricity damage, 1 target w/i 45', requires ranged touch, no save