Okay, here it is- warning it is not as 'crunchy' [that is has hard and fast numbers] as I like but it's a step in the right direction I think-
From "Raven's Rules of Sorcery v 1.1'
Revised ability
Final Strike [was ‘Defensive Blast’]
[Note- this is the second version of this effect I have created, but I am still tinkering with the effect in gameplay. Let me know what you think might be an improvement]
Final Strike is an optional set of rules designed to replace the Defensive Blast ability of sorcerers. It is available at the first level of Scholar and thus is not usable by Dabblers or creatures with spell like powers.
Sorcerers have access to the arcane forces with themselves and from sources unfathomable to the vast majority of humanity. Normally, they must handle this power with care, controlling the flow so as not to burn out their mortal bodies with the vast and powerful fields of power they manipulate through themselves. In desperate times and need though, a sorcerer may have no choice but to upset this delicate balance and tap the raw uncontrolled forces of magic unchecked.
When executing a Final Strike, a sorcerer releases all the Power Points he or she currently possesses into one spell or spell like effect. This power can take a number of options.
1) Final Retribution The classic version of Final Strike, the sorcerer channels the raw force of magic into destructive effect. The type of power is determined by the primary Spheres of Power utilized by the sorcerer. For example necromancer skilled primarily with the Death and Destruction Sphere would produce a black energy that sucked the life force out of those affected, a elementalist with Elements and Forces with a knack for fire would create the classic fireball and a practitioner of Life and Nature would create swarms of vicious insects and animate vines to choke the life out of people and devour inanimate structures,
The sorcerer utilizing Final Retribution must select a target area for this effect. The sorcerer must make a ranged touch attack against a target area. All areas has a base DV of 10 and the effect has an effective range increment of 10 feet. Targeting your own position is an automatic success of course. If the ranged touch attack roll hits, the area targeted is the center of the effect. If it misses, the target of the effect is an area within 20-120 [2d6 x 10] feet away in a random direction.
Once the target of the effect is determined, the effect begins. Final Retribution is an unchecked flow of power designed to rip apart the very primal pattern of the world around it. The effect lasts for 1 round per Power Point expended by the sorcerer. In the first round all creatures, objects and structures at the targeted area receive 1d6 points of Primal [i.e. ignores all non magical DR and Hardness]
damage. [Living creatures may make a Fortitude save to halve the damage to a minimum of 1] Each round thereafter for the duration of the effect, the effect spreads outward in a 10’ radius affecting all within that area with 1d6 additional points of damage each round. [Save for half as above] The affected area continues to expand an additional 10’ each round until the effect ends. Note that swiftly thinking [and moving] creatures can move to escape the effect once they are aware of it, though most immobile creatures, structures and landscaping will likely be devastated.
This effect is the source of the ‘castle falling about the hero’s ears after he kills it’s master’ cliché and is likely inspired by Sauron’s death scene at the beginning of Fellowship of the Ring. The end result is more damage over the original version, but at a slower rate that allows characters a better chance at survival. Immobile characters, structures and objects at the center of the effect will likely be pulverized when enough PP is expended.
2) Final Curse Another option is for the sorcerer to channel all their Power points into a long lasting ‘Death Curse’. The sorcerer chooses a spell from the Blight and Curses Sphere of Power [or with the GM’s approval, a spell from another sphere if deemed appropriate] and empower it. The sorcerer must have at least enough PP remaining to cast the spell normally. The spell is cast immediately on a applicable target of the sorcerer’s choice.
If the sorcerer has PP in excess of the spell’s normal cast, they can use the excess PP to make the effect stronger. For each PP in excess of the regular cost, the sorcerer can choose to add +1 to their Magic Success Roll, extend the duration of the spell 25% or add 10 ft to the range of the spell to affect someone normally out of the range of the spell. [Note that Touch range spells have a effective range of zero and may be boosted in the last example] If the there is enough PP to cast the spell again, the caster may designate another target to affected by the spell as well as if it had been cast separately at them. [Note that in this case, the Rule of Success allows the caster to only need one half the PP cost the curse on the second and subsequent targets if successfully cast on the first] The caster may keep recasting the spell on additional targets so long as they have PP left.
Note that the above options are only available for a sorcerer committing a Final Strike. At no other time may the sorcerer extend the effect of their spell without the appropriate Feat and/or environmental effect.
3) Final Spell As above the sorcerer can channel all their Power Points into a spell, but in this case, the spell need not be a curse. In this case, the sorcerer may modify spell using the same options as given in ‘Final Curse’ above within reason. GMs would have to decide what effects would appropriate, A sorcerer using a boosted summon undead horde to create a large mass of hungry, uncontrolled Risen Dead is very appropriate. Using it to create a long lasting witchfire effect is just silly.
4) Final Gift Not all sorcery is dark, nor all sorcerers power mad imbeciles with childhood issues. Heroic sacrifice is a cornerstone of fantasy fiction, even in the Hyborian Age, A sorcerer may channel their Power to create a beneficial effect such as a healing spell, a final prophetic vision or communicate a dire warning with the Communication and Divination sphere or to give another character a +1 bonus to an attack roll, saving throw or skill check. In addition they can pick a spell from the Blessings and Protections Sphere to act as a ‘final blessing’ which can be boosted in the manner of Final Curse above.
With the GM’s approval create a less ‘rule-orientated’ effect like creating a spring from bare rock that acts as a minor healing spell to those who drink it, fertility and prosperity to an area for years to come or to bind themselves to the material world as a Guardian Spirit ala Obi Wan Kenobi. [In the case of the last option, the spirit becomes a NPC controlled by the GM]
The Price
Final Strike is usually as final as the term suggests. Channeling uncontrolled energy threatens to tear apart the body and soul and often kills the sorcerer using it. To survive the use of a Final Strike effect, the sorcerer must make a successful Fortitude saving throw against a DC equal to 10 + the amount of PP expended. If failed the sorcerer dies immediately. If the saving throw is successful, the sorcerer is reduced unconscious, at 0 hp and to 1 in all attributes and must recover naturally. [Note- If the sorcerer somehow managed to use Final Strike at below 0 hp, Final Strike automatically kills them.]
Further more if the sorcerer rolls exactly the DC of the saving throw they survive but the metaphysical stress placed on them has destroyed their ability to use magic forever. They retain their magical knowledge and can train others, but can never cast a spell or hold PP in their lifetime without legendary difficult measures. [The quest required to recover powers lost in this manner would make a good adventure in itself 8)]
Fatal Strike
As a further option, a sorcerer may choose to automatically fail their Fortitude check [and thus die] to add their lifeforce to the Final Strike. The effect is as if the sorcerer sacrificed themselves to provide PP to the Final Strike effect. A sorcerer who lacks the Ritual Sacrifice Feat gains 1 PP for each 8 hp they have remaining, while one with the feat gains a PP for each 4 hp they possess at the time. Bleed Dry provides the usual effect- the sorcerer may utilize the 10 hp between 0 and –10 in the effect, but few sorcerers would have the time [or be crazy enough] to utilize the Tormented Sacrifice Feat on themselves 8).