For the record Magic Screen at PL 1 provides +11% magic resistance for all realms, and 4% for each PL above.
Clearly visible on a characters Magic page


Pretty sure the 1.24 exe only does not show resistance values above 100,
and takes values up to at least 125 into account,
and that at some point its capped and wraps around to zero.

1.26 exe and above allow to show resistance values of up to 200,
not sure if the code was also revised in order to allow 200,
or if thats also the actual limit in 1.24


Powercast raises the dmg output of spells(above the spells nominal dmg output!)
by ~25% for a PC value of 100.
Based on ingame observations using caster ~15lvl above target
(i.e. resistance piercing capability of PC had close to zero effect on numbers)

It affects more than just damage. In particular:
* Healing is affected. This means that, if you want the most powerful party-wide heal, you need high Power Cast on a character with Priest spells (Priest, Bishop, Valkyrie, Lord).
* Combat only support spells are also affected. This includes Haste, Superman, and Element/Soul Shield. (Is Slow also affected?)
* Even Identify Item is affected. (Identifying a Renewal Potion only needs PL4 with enough Power Cast.)
* (Does Power Cast boost the effects of backfired spells?)