Hi! I've just discovered Pathfinder and I think it's amazing! An advice, though.
I'm taking the Elemental Spell metamagic feat that allows me to change the type of damage of the casted spell for a once selected energy type. It's in the APG page 158.
Since I obviously want to take the feat only once and considering I'm a blastish sorcerer in a campaing in the Underworld, which energy should I choose? Which is the less frequent elemental resistances among monsters?
Since I'm already asking... Wall of Stone or Wall of Force?
Tank you all in advance!
It has been my experience that fewer monsters have a resistance/immunity to electricity than they do to fire and cold.
Ergo, I would sling the lightning if I were you.
you didn't say but if your playing wizard there are new spell schools admixture is one that lets you change the damage type of your spells and unlike the feat its not 50/50 old new damage type it cponverts 100% to the new damage type.
strong acid resistence is also less common
as for wall of stone vs wall of force
wall of stone if you want to trap things for extended persiods of time, wall of forc if you want to break up an encounter but not block yourself.
example walk into a square room see 20 enemies who start running towards you, cast wall of force to cut the group in half deal with the first 10 and by the time the wall comes down you'll be ready to deal with the next 10.
wall fo force is also good for blocking reatreats that you'll want to use later.
wall of stone is more permanent which is requred less often, but you may want to use it to make stone bridge to enter a dungeon and your going to still want it there when you come back.
Sonic is the rarest among true energy damages, but it's also very hard to get access to. Acid is probably the rarest of the 4 you can pick with Elemental Spell. Force is the rarest overall (Only a handful of monsters ever published for 3.0, 3.5, or Pathfinder by any publisher have any resistance or immunity to force).
Generally speaking, from least resisted to most, it's force > sonic > acid > electricity > cold > fire. Since you can't pick force or sonic, though, acid is your best bet...but when you say "Underworld", do you mean the Darklands (Underdark), or like...the Abyss/Hell/etc.?
Because if it's the latter, you're gonna run into a ton of elemental resistances among fiends, and depending on which type (devils, demons, daemons, or whatnot) you may want electricity instead of acid (definitely not fire, though, and pretty definitely not cold - a whole bunch are flat out immune to those two).