Magic Resistance Formula?

[Zapmeister]

Has anyone figured out the odds of success of a spell cast with penetration P that has found a target of magic resistance R ?

[Nagot Gick Fel]

Originally posted by Zapmeister:
Has anyone figured out the odds of success of a spell cast with penetration P that has found a target of magic resistance R ?

My guess is it's (10 + P + 1D6oe) vs (R + magic bonus + 1D6oe).

1D6oe = 1 six-sided die, open-ended.

P = attacker's penetration, includes bonuses from items + (extra magic skill / 2)

R = defender's MR, includes bonuses from items or spells like Iron Will.

magic bonus: applies if the target's is skilled in the path that's used against it - eg, a nature mage will resist Charm better, an astral mage will resist Soul Slay better. I'd say this bonus is magic skill / 2 (rounded up?), but it's just a guess (hard to test thoroughly because of the open-ended random factor).

[Kristoffer O]

2D6 (oe)

[Graeme Dice]

Originally posted by Zapmeister:
Has anyone figured out the odds of success of a spell cast with penetration P that has found a target of magic resistance R ?

It's in the first post in this thread.
Dice Roll Chart

[Nagot Gick Fel]

Originally posted by Kristoffer O:
2D6 (oe)

I assume this means the rest is correct, including the 'magic bonus' part?

[Kristoffer O]

Yep. Not entirely sure of the rounding up, but I believe it is up.

[Saber Cherry]

I understand that base penetration is 11, or 7 for an "easily negates" spell. So casting a normal "magic resistance negates" spell with no penetration boost versus a normal MR 10 opponent would put you in the "0+" row with a 54% success rate. 2 additional levels in that spell's path give you a +1 penetration, for 62%, and adding a spell focus gives +2 penetration, for "-3+" 76% success.

The row is determened by the minimum roll difference required. So penetration 11 versus resistance 10 requires a roll difference of 0 or greater, as the penetration has to BEAT, not just tie, the resistance.

-Cherry