What were my expectations from Power Cast, was that any and every spell would become more potent.
Even spells like Bless (that have in description, the casting level only impacts duration, but I still hoped that Power Cast might even boost the seemingly 'locked' stats of Bless)

Note, that I had no clue about actual calculations, on how various spells work, so I could only observe from experience, learning, that on some spells Power Cast has impact, on other it does not.

Yet, my undying hope was still the same - for example Light would shine brighter, Lure would work even on farther critters, Magic Screen would not only last longer, but possibly even add extra resistance (even beyond 100 cap). Offensive spells would pierce/penetrate natural resistances plus deal more damage.

Power Cast, with other skills of the same category (get unlocked first after respective STAT reaches 100), were basically giving an "ultimate" feeling, promising kind of upper hand over the ingame enemies. Especially after I started noticing, that pure spell casting classes become gradually less effective, to an extend, that even 3 spell in a row dealt 0 damage, virtually rendering such classes useless (especially considering those had the worst HP pool and defenses/armor)

Fact is, that Priest, just like many similar classes (hybrid), often have not drive to spend points on INT -> subsequently never unlocking Power Cast. But would Power Cast give a clear promise of boosting EVERY spell, even Priest with his Falling Stars or even Banish (so useful in some areas) might consider investing into INT just to unlock Power Cast.

Even if not great offensive warriors, both Priest and Bishop are steadfast vanguards, literal tanks, who can withstand tremendous array of attacks as magical so physical, hence apart Piety, one might desire to invest into Vitality.

Ironically, Priest sub-classes, like Lord, might benefit from INT, as it does impact several offensive skills. But still I would rarely focus on INT as the first 2 primary stats, that needs to be increased to 100 while training Lord or Valkyre.

Which is probably why Power Cast was not that boosting for Priest Spells, to not make players torn apart during character customization and level-up planning.

Maybe it never had to be in scope of single skill - Power Cast, but some extra skill could have been added, that would help spell casters get through resistances (it could have even be made unique, dedicated only to few rare artifacts, instead of and generally achievable skill)

Just like there are melee criticals, throwing criticals or ranged criticals, some spell caster could have spell critical (that instead instant death would reduce targets' resistances in an extended depending from skill level)

What effect would you expect Power Cast to have on, say, Set Portal?

Power Cast does boost some things you might not expect:
* The duration of Light, which is otherwise fixed
* The power of Identify Item, causing it to sometimes be cast at a lower power level than would otherwise be necessary
* Haste and Superman are affected, as is Body of Stone, making it easier to reach 100% DR (though still not sufficient by itself, I believe)

Powercast of 100 raises dmg output of the dmg spells by 25%, compared to casters with otherwise identical stats but zero PC.
Tested with characters of various lvls casting specifically designed spells which had fixed dmg instead of a rng range,
on targets of lower, somewhat equal and substancially higher lvl, with resistance range from 10 to 255.

Additionally PC almost certainly helps to overcome the targets lvl and resistance,
although thats hard to prove for spells with a side effect like insanity, paralyze etc.

Pretty sure it boosts every spell, and almost sure it does "only" affect either dmg or otoh duration of buffs or side fx, but not both.

Realm skill appears to also have impact on overcoming target resistance/lvl,
bc the mage gets highr avg dmg output for castin same spell at same PL than the bishop,
but thats from observation only, not a tailored test scenario like for PC

Portal could offer extra memory slots.

That would require an entirely new interface, and wouldn't be something that could see contiunous improvement.

The only sensible way the spell could offer multiple slots would be to tie it to the spell's power level, so a PL3 Return to Portal would take you to where PL3 Set Portal was cast (and would give the "impossible" message if you haven't cast Set Portal at that particular power level).

It doesn't make sense for Power Cast to improve this particular spell.

Well yeah, but as I stressed out before:
A) I had no clue about actual spell-coding, code-weaving in the layer of game mechanics
B) There was a very simple expectation / hope, that all spells would become more potent with Power Cast (so I could not possibly have guessed how Portal is coded, and hence could not have an educated guess what to expect exactly, just better)

On other hand: if a spell cannot become more potent due hard-coding, it can become cheaper for example.
Or when looking at other similar games: the same spell can exhibit different behavior based on PC:

Power Cast 0 : spell works only when all characters are alive and conscious and no enemies are nearby
Power Cast 1~24: Spell will work also with some chars unconscious, but not dead and still no enemies may be nearby
Power Cast 25~49: Now status of characters does not matter, but enemies still cannot be nearby
Power Cast 50~74: Enemies can be nearby, but does not work during combat
Power Cast 75 ~ 99: Works in Combat under any conditions
Power Cast 100 ~ 124: Portal costs 50%
Power Cast 125 : Portal is for free

The suggested teleport advantages provided by Powercast are in no way offset by disadvantages,
especially the fact that the spell is no longer combat-only.
It would be different if monsters could track the party with teleport.

My counter-proposal would be to treat this similarly to D&D 1st Edition.
Without PC skill, for example, there's a 10% chance that the teleport will land too high above the intended target
(i.e., if it's above the ground, fall damage will occur) or too low, which usually leads to an immediate wipe.
With increasing PC value, the chance of failure decreases logarithmically and is zero at PC 100.
As a gimmick, we add a chance that party members will be healed from ailments, starting with PC skill of e.g. 10.

Sounds like fun, could be really intriguing to have such spell behavior implemented :)

There were few games that had random misplacement implemented for teleport (and subsequently had also recovery spell, that could bring unfortunate party out of dungeon wall, then de-petrify them and then resurrect them, but only if they were not trapped there for way too long, then more expensive spells were needed )

Teleport that heals and cures, sounds fantastic. One would desire to have it combined with ad-hoc teleport (instead set portal -> return, just teleport during combat to any visible and free spot, and get cured in the process)
Which reminds me : there is Heal All, but not Cure All in W8. ( Remove Conditions All )

As a reminder, back in the old days (Wizardry 1-5), you had a spell that could teleport you wherever you want (excluding no-teleport areas like the final floor).
* Catch is, you have to specify how far you want to go in each direction.
* Teleport into the moat (anywhere on level 0 except (0,0)), and some of your party members will likely drown (instant death).
* Teleport above the caster, and your entire party falls to their deaths and dies.
* Teleport into solid rock, and your party is lost forever.
Ultima 6 and 7 does this, though it can only teleport you to one specific location. It seems that the spell in question, which is cheap and requires no reagants (unlike every other practical spell in those games), exists so that players wouldn't intentionally die in order to death warp.

Many Japanese Wizardry spin-offs (starting with Wizardry Gaiden 3, where it's a 5th level Alchemist spell) have a spell that will cure your entire party of status ailments. The version in WG3 will even cure poison and paralysis, but not petrification. You see that effect in the Elminage series (including Elminage Gothic) as a 5th level Priest spell (with a weaker 4th level one that's basically that game's Mass Cure Light Conditions spell).