The basic idea was to use RQ3 sorcery, but without MP ( :shock: ), but instead based on 'drawing mana' from the surrounding as in TW.
1) Choose Spell effects as per RQ3 sorcery and get total casting cost and casting chance as normal (based on intensity, duration, etc).
2) Caster can safely draw mana equal to something (either POW or total casting chance/5, hadn't really decided). If draw mana above and beyond that each additional Mana Point costs 1 HP rather than FP (see step 3 below).
3) Roll casting (on casting base SR). If a success one 'MP' worth of mana is drawn for the spell for each full 10 points you roll. On a special it is max for your skill, on a crit double max. Lose 1 Fatigue point for each MP Drawn (but not on specials or crits). If the Mana is drawn above the casters ability, lose 1 HP instead.
Once the total Mana required is drawn the spell goes off on the casters SR (so low powered spells might even go off instantly). If the total is not reached roll again next round (on Dex SR) and continue drawing mana.
You never 'overdraw' mana. If you only need 3 to cast a spell, and roll enough to draw 6, you only draw 3 and lose 3 FP.
On a failure the round is wasted but the casting is not aborted. I had considered something like failing by more than 20 casing the spell to fail.
On a fumble the caster takes damage to Total HP equal to the mana drawn so far, with a roll (probably POWx5) to halve the damage. The spell fails.
I went with RQ3 because it seemed a better fit with the FP and total HP, but something could be worked out for MRQ (increasing fatigue levels and random location damage or something like that). RQ3 is deadlier too, which fits TW pretty well.
Example 1: Bob casts a Damage boosting 5 with duration 2 (total magnitude 7) and has a final casting chance of 45%. On his first round he rolls a 22, so he draws 2 of the required mana and loses 2 FP. Next round he rolls an 88, so no new mana is drawn, but he can continue casting. On the third round he rolls an 07, a special, which means can draws 4 (the most he can draw with a 45%) but loses no FP. He is still one shy, so continues casting. Next round he rolls a 37, which would draw 3. Bob only needs 1, so he casts the spell on his Dex SR and loses 1 FP.
Example 2: Xerxes has a Damage Boosting 92% and Intensity 88% and decides he wants to cast Damage Boosting 7. He rolls an 82 - Nice. The spell goes off instantly on his Dex SR and he loses 7 FP.
This is a bit RQ3 centric for the MRQ Wiki (but may work well with the new BRP). I'll try to convert to to MRQ rules and post it to Mr. Qwiki - but feel free to run with it first if you beat me to it (and real life has been keeping me busy lately).