From Krakiipedia, the unofficial free GemStone IV encyclopedia.
Spellburst is a balancing mechanic for higher level hunting areas to manage the amount of outside spells a character can wear in the areas that Spellburst effects. Those areas are the Keen, including Wyneb Temple, (Skull temple,) Old Ta'Faendryl, and the Ruined Temple, (Nelemar) on Teras. Failure to observe this feature can result in outside spells being violently torn from the player, causing HP and critical damage, and possibly resulting in the character's death. Training in magical skills will help to increase the amount of outside spells a character can safely wear in a spellburst enviroment.
The following formula seems to be accurate up to half your level in wearable outside mana. It is well known that the current formula goes bogus once the result is over half your level in wearable mana.
All values are Skill RANKS, not Skill BONUS.
Wearable mana = ((AS + MIU + HP + SA) + 0.5(Controls + lores)) / (225 / level)
Worn mana should be calculatd as follows:
No known spells will be counted toward your worn mana total.
Learnable spells have their mana values halved for spellburst calculations.
Certain spells are weighted heavier than other spells. For instance, elemental spells seem to burst 0.5 mana sooner than spiritual spells. Spells with a spellburst mana cost of 9+ seem to be extra volitile as well. Examples are strength, blurs, mobiles, bravery, heroism.
GROUP spells do NOT count toward spellburst. Mass spells, however, do count for spellburst. Also, offensive spells that show up in the SPELL ACTIVE list do not count toward spellburst. The following is a list of spells known to show up in the SPELL ACTIVE list that do not count toward spellburst.
Level 75, rogue, 24 AS, 24 MIU, 31 HP, 20 SMC, 20 EMC ranks, knows to spell 404.
In order to determine the wearable mana of this rogue, we plug the numbers into the formula.
((24 + 24 + 31) + 0.5(20 + 20))/(225 / 75) (79 + 20) / 3.0 99 / 3.0 = 33.0 wearable mana.
- I intentionally selected a skill/level set that would generate an end result that is less than half the level in wearable mana.
Assume once that that same level 75 rogue had... 30 AS, 30 MIU, 40 HP, 20 SMC, 20 EMC ranks... the formula would generate 40 wearable mana. At level 75, the formula is only accurate up to about 37.5 mana, so that "extra" 2.5 mana is really more like... 1 mana. I haven't gathered enough data to actually crack the next step.
Assume this rogue capped without gaining any relative magical skills....
The initial skill set...
((24 + 24 + 31) + 0.5*(20 + 20))/(225 / 100) = 49.5 wearable mana.
The secondary skill set...
((30 + 30 + 40) + 0.5*(20 + 20))/(225 / 100) = 60 wearable mana.
The initial skill set generates a value lower than half the level in wearable mana, while the second generates a value more than half the level of the character. That said, the wearable mana is probably more like, 52 wearable mana. Again, I just haven't been able to solve the next step of the formula.
Let's assume we are dealing with the initial skills set of the level 75 rogue with 4 minor elemental ranks. The wearable outside mana came to be 33. It is important to manage what spells fill that 33 mana, as some spells are quite costly with minimal benefits. Since both the 100s and 400s circles are learnable by the rogue, it's probably best to add those spells first. 101, 103, 107, 406, 414. Those spells, all combined have a mana value of 31, 15.5 when halved. Subtract that from the initial 33 total, and we have 17.5 mana to add. If you have 601, 202, 503, 509, that's a quick 15 mana, leaving 2.5 extra wearable mana as a buffer, which is good.
In closing: The information above is as accurate and simply put as I can give it. There are some gray areas in the research, and the formula, and in how to calculate each individual spell value. Spells that constantly cause oddities for me were 509, 911, 215, 211, 219, 618, 313, 913, 513, off the top of my head. Simply adding 0.5 mana to their base value seemed to help remedy some of the problems with the calculations. Good luck! Burst less!
Information and testing provided by Gibreficul