if magic items were excluded from the game, what monsters would also need to go?

[vasilidor]

exactly the question on the title.
and at what point do some monsters become feasible foes? the basic CR system assumes that at certain levels you will have X amount of magic boost, like this for example: https://www.d20pfsrd.com/gamemastering/other-rules/unchained-rules/automatic-bonus-progression/
in this question I assume that this, and other fixes like this, are not being used either. thinking about it some more, it becomes apparent that the shorter list may be what monsters can the characters face?
we can probably through out almost all slimes, ethereal or incorporeal monsters and quite a few outsiders.

[Crake]

exactly the question on the title.
and at what point do some monsters become feasible foes? the basic CR system assumes that at certain levels you will have X amount of magic boost, like this for example: https://www.d20pfsrd.com/gamemastering/other-rules/unchained-rules/automatic-bonus-progression/
in this question I assume that this, and other fixes like this, are not being used either. thinking about it some more, it becomes apparent that the shorter list may be what monsters can the characters face?
we can probably through out almost all slimes, ethereal or incorporeal monsters and quite a few outsiders.

If spellcasters are still on the board, then the answer is none.

No monster is unbeatable without magic items. Slimes that split can be bludgeoned to death, ethereal and incorporeal can be beaten using serren wood, DR/magic can be overcome with cyrite, alignment DR can be overcome by casting polymorph into creatures with alignment subtypes, or a few various exotic materials.

With sufficient intel gathering and preparation, any monster is beatable, they just become challenges that you need to think about more carefully than simply rush in, kill monster.

[Epic Legand]

When removing magic items, you are further pushing the balance of power to casters.
+1,+2,+3 ring of pro...not much of a difference, just better...but basically the same options and choices.
Push your fighter off the griffon, now we find out who can cast feather fall, and who wishes they had a ring.... of feather fall.
your 10th level sorcerer ( the caster choice with the LEAST options)...has 15 different spell slots without any magic items, feats or racial options. Each one a potential game changer. Pick a cleric or wizard this disparity is far worse.
The automatic progression is a trap that further imbalances martials.
If you though a 10lv caster had a point value of 400, and a 10th level martial had a value of 200, that would be an extreme imbalance. If you removed 100 points from both, someone would claim it equally gimps both...but that would be a fallacy. One side is more hurt by the removal of choices then the other. Just ask the guy who used to ride griffons.

[Quertus]

At sufficiently high levels of optimization, the answer is "nothing". So the real question is simply how much more optimized do characters (especially muggles) need to be to cope with a GM unbalancing a game more by excluding magic items?

[Vizzerdrix]

Casters, but that is a different problem all together.

[Blue Jay]

Good DMs make every effort to match the game to their players' play style(s). So, if you're a DM who wants to take away magic items, you need to be aware of how that will impact the party's ability to meet game challenges, and how it will alter balance among party members. You're probably not going to get it exactly right, so you just need to make sure you and your table are willing to deal with the uncertainties and errors you'll make along the way, and that you're flexible enough to adjust the game on the fly.

But, the bottom line is that you can't expect to make a big, sweeping change like taking away magic items, and still run the same game in the same way. You can probably still run any monster you want, but you likely won't be able to run it the same way or at the same level you would run it otherwise. And you'll probably need to make changes like running lower-level adventure modules, point-editing modules to exclude or adjust some content, and/or giving out different kinds of boons to compensate for the lack of magic items.

I only DM online, in play-by-post format, so that gives me plenty of time to make this kind of adjustments mid-game. For live games, adjusting on the fly is obviously more tricky. You'll need to do a lot of prep work ahead of time to make sure the encounters and challenges you've planned are appropriate for your table, and to build in enough flexibility to allow on-the-fly adjustment.

[vasilidor]

even with the caveat that spell casters make it so that you do not actually need to eliminate any monsters, I think that the CR equivalent of many monsters would be altered, even if for no other reason than game math. the CR of monsters is calculated based on the assumption that a given amount of magic items will be available at a given level, which is where the wealth by level and the afforementioned automatic progression chart come in.