[Taqwus]

Hm. If there is a penetration bonus (which does seem likely), it should have been mentioned in the documentation. Spells easily resisted, after all, get marked as "Magic resistance negates easily" (4 pt. penalty, for base penetration of 7 instead of 11).

Could indeed be +4, that'd be symmetric. Base penetration of 15 + (magic-required)/2? If you want more penetration, Rune Smasher and Spell Focus each give +2, and the sorcery and wizardry rings each give +1. (A Crone, with three misc slots, could thus get +6. Ouch. No armor, 'tho; might want to use Amon Hotep or an invulnerability spell.).