Golems. A grab bag selection of opponents that have roots in both Jewish mythology and 19th century gothic horror, golems have a long history in D&D as the servants of casters, constructed from whatever happened to be lying around. Mindless but powerful, the elemental spirit that powers a golem renders it immune to all but a small selection of magic depending on its composition (golems made from clay or stone are vulnerable to spells that move or alter stone and earth, for example) as well as non-magical weapons (or even less potent magical weapons in the case of the more dangerous iron golems, who required +3 weapons or greater to harm them). Though unintelligent and physically slow, their physical power, host of immunities made them a challenge to face in combat for all but the most skilled of warriors.
And then we get to 3e. In 3e, the weapon immunity of monsters was
replaced with Damage Reduction, which took off a certain amount of your
damage if you didn't have the right weapon. In theory, you could power
through the DR and still do some damage with a big enough attack. And
this worked with creatures who had DR 5, 10 or 15, but when an Iron
Golem had DR 50/+3, you weren't even going to scratch it without a huge
attack (especially since golems are immune to critical hits in 3e since
they have no vital organs to stab). The Iron Golem's DR 50 was
admittedly an outsider by 3.0e standards, even the Tarrasque itself had
only DR 25/+5.
With 3.5e, they decided to wind back Damage Reduction so it no longer
required a certain magical bonus or better, likening it to an amusement
park sign that said "you must be at least this tall to fight the
monster" and admitting that DR numbers were probably way too high to
make things fun without the right weapon. Thus, they wound back the
numbers and focused more on things like your weapon's material
composition. So the iron golem went from DR 50/+3 to DR 15/adamantine.
Of course, the thing about material-based DR is that things get
annoying when you have to carry three different weapons to deal with DR
that requires Cold Iron, Silver, or Adamantine but at least it wasn't
quite as high.
One other interesting thing about golems in 3.5e- they went from
"[GOLEM] is immune to all spells, spell-like abilities and supernatural
effects" (barring exceptions that followed) to "[GOLEM] is immune to any
spell or spell-like ability that allows spell resistance" (usual
exceptions that followed).
Spell Resistance is the innate ability of certain creatures to resist
spells cast on them, requiring a certain degree of luck/magical skill to
pierce through it, represented in the form of a caster level check
(1d20 + your character's caster level + any additional bonus from feats
or your anime kimono and the like) against a target number, with the usual assumption
that most monsters will have their SR breached by an on-level caster
about half the time. Golems effectively have infinite/unbeatable spell
resistance (which is similarly used with the Spell Immunity spell).
Imagine a car on a long road trip with two kids sitting in the back.
After a while, boredom sets in and Kid A starts poking Kid B in order to
get a reaction. Kid B complains, and the parents tell Kid A to stop
touching Kid B. After about a minute, Kid A picks up a crayon and
starts poking Kid B again. Kid B complains once more, only for Kid A to
say "What? I'm not the one who is touching you, the crayon is."
Now imagine that the parents agree with Kid A's analysis and tell Kid B
to stop whining, and you'll have an accurate model of a wizard's
relationship with Spell Resistance.
Spell Resistance can be an effective defense against magic that directly
affects a target, but offers no real defense against indirect spells.
So SR will protect you against being disintegrated or lifted by telekinesis, but it won't prevent a wizard from using those same spells to disintegrate the floor beneath your feet or throw a boulder at you.
But the thing is, a wizard doesn't even have to be all that creative in
order to circumvent SR, as there are plenty of spells that simply ignore
SR altogether. The majority of them are Conjuration spells, operating
under the assumption that SR doesn't matter if a wizard summons a rock
above your head- you're still going to get hit by a big old real rock.
Of course, this assumption is stretched to its limits when you start
comparing conjuration to evocation spells- a line of ice spears created through conjuration bypasses SR, while line of ice slivers created through evocation
does not. This is because the conjuration spell is a conjuration
(creation) spell which "creates objects or effects on the spot", while
evocation merely manipulates magical energy "to create something out of nothing".
Insert hand-wavey explanation about how it's fine because evocation
offers a higher potential for damage and it makes sense because magic.
But direct damage is for chumps, let's play with the real stars of the spell list- debilitating status effects. Grease creates a zone of control that knocks creatures on their asses if they fail a Reflex save, Glitterdust blinds targets for one round per level if they fail a Will save and thwarts attempts at hiding, while Web
ties down anyone who gets caught in the area. All three are low-level
conjuration spells that ignore SR. If you feel like stepping it up, why
not go for a "no save, no SR" conjuration like Solid Fog or add in some pepper with Acid Fog
so you can murder your foes as you keep them unable to attack or move
much. Pathfinder decided that the no-SR conjuration list wasn't quite
complete and introduced the fun line of extradimensional trapdoors
starting with Create Pit, and allowing you to upgrade to add spikes, acid,or thrashing walls, with each upgrade increasing the maximum depth of the pit.
Well, you have a host of spells that can bypass a golem's immunity, but
that doesn't necessarily mean that you're going to be able to beat the
golem, right? Monsters and 3e/PF are designed by giving them class
levels if they're humanoids (usually), or hit dice of a respective
monster type if they're not. Monster hit dice are like character levels
in that they determine things like hit points, skills, saves and attack
bonuses. In the case of a golem, it uses construct
hit dice, which provide a good BAB and d10 HP like a fighter, but while
a fighter has a good Fortitude save but poor Reflex and Will saves, a
construct has no good saves whatsoever.
A creature's saves are further modified by its ability scores, so let's
see how things stack up. Fortitude is modified by your Constitution
score, but as constructs aren't alive, they have a Con score of "-",
which is treated as a +0 modifier. Reflex is modified by your Dexterity
score, but golems are slow and plodding, so they don't have good Dex
scores, with most having negative Dex modifiers (with the exception of
the mithral golem).
Will is modified by your Wisdom score, but as golems aren't
particularly known for their wisdom either, they tend to have scores of
10 or 11 for a +0 modifier. So their Fort, Ref and Will saves start
shitty and go nowhere after that. This leads us to the once-dreaded iron golem, a monster suitable for a 13th-level foe whose saves top out a whopping +6 Fort, +5 Ref, +6 Will- which would have been impressive for a 3rd level foe and underwhelming for a 7th level foe. Its adamantine big brother
isn't much better, a 19th level opponent with saves appropriate for a
7th- to 11th-level opponent. Thus the odds of the golem blowing its
saves toppling blindly into a deep acid pit are pretty damn good.
Because a golem isn't living, it doesn't have a Constitution score and
thus doesn't get bonus hit points per hit dice, with only a generic
construct size bonus to HP, thus our CR 13 iron golem has HP appropriate
for a CR 11 monster, and the CR 19 Adamantine Golem has HP appropriate
for a CR 14 monster. There's still the DR/adamantine to deal with for
the iron golem (and DR 15/epic for the adamantine golem, requiring a +6
or greater weapon to deal with it), but fortunately Pathfinder allows
for +3 or higher weapons to overcome DR based on their enhancements even if you're not packing the right weapon (though getting an adamantine weapon is just a good buy- only 3000 gp
for the ability to carve stone or steel like butter and make it more
difficult for opponents to damage your weapon in return). Additionally,
golems in Pathfinder are no longer immune to critical hits and sneak
attacks. So assuming you can save yourself from being punched in the
face by a golem's heavy blows, mid-level characters should have little
trouble carving its lackluster HP count to pieces.
Golems not only aren't living, but most are also mindless as well and
thus have an Intelligence score of "-", which means that don't get any
feats or skill points whatsoever. So you might want a powerful
adamantine golem to stand an eternal watch over your hidden fortress,
but with no Wisdom modifier and no skill points, your adamantine golem
has a Perception score of +0, meaning it's as valuable of a watchman as
Mr. Magoo. Even if a first level character could be killed by a single
attack, that character could still have decent odds of being able to
sneak by or deceive the golem, and once the character hits +20 or more
to a skill check, the golem basically can't win no matter what comes up
on the d20. No skill points also means that its jumping and climbing
abilities are absolutely terrible, so if it falls into a hungry pit
it needs 40 strength to have even a 5% chance of climbing its (quite
slow) speed every round (with a 20% chance of doing nothing each round
and a 75% chance of losing all progress and falling back down to the
bottom). A lack of feats also means a lack of any combat options more
sophisticated than "golem smash" or any feat-based way of shoring up the
golem's abysmal saves.
What was designed to be a terrifying unstoppable murder-bot
turns out to be a foe that can be trivially thwarted by throwing
glitter in its face and watching it fall down a hole. Golems are pretty
much what happens when you turn the Terminator into a Home Alone villain.