Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Some immunities from gear, sure. Specifically for intelligent creatures, like giants, who can and do equip gear like players can. Which is why I don't mind the FGK for example having a ring of fire resistance. It makes sense he'd try to combat his vulnerability to fire.

But they should not have every immunity under the sun. And in many cases, it should come from buffs, not items, so it can be dispelled. The occasional item immunity is fine, but it should be the exception, not the rule.

The kinds of things that could be used to give bosses goodies, instead:

http://www.d20srd.org/srd/epic/magicItems/armor.htm
http://www.d20srd.org/srd/epic/magicItems/rings.htm
http://www.d20srd.org/srd/epic/magicIte ... sItems.htm

If you wanted to make bosses a bit more unpredictable (and hence a little more difficult) why not give them 4 or 5 spots it’s possible for them to spawn in, make them areas that give them a tactical advantage if possible.
If players know the FGK will always spawn in the throne room they can plan accordingly (short term buffs, hit/run tactics, etc).
If players are romping through the frost giant keep mowing down minions and they run around the wrong corner unbuffed straight into a buffed and ready FGK and his minions it makes things difficult.

It used to happen with the Ogre Chieftain ages ago - kept you on your toes and made it so you couldn’t waste short term buffs until you knew where the boss was.

Ewe wrote: ↑Thu Sep 23, 2021 2:24 pm 1. What's the difference between a boss and any other monster supposed to be?

A leader, or otherwise powerful figure among your enemies. In PnP, these would usually be named characters, or small groups of named characters, who were considerably more powerful than their peers.

In the Order of the Stick comics, these would be Lirian, Dorukan, Xykon and Redcloak, the "Young Black Dragon" (and technically his mother later on), the ghost of Soon Kim, arguably the Linear Guild and Vector Legion, the High Priest of Hel, the Exarch, Serini and Sunny... all of them noticeably more powerful than random goblins, and all of them having interests that place them in direct opposition to the Order.

In the campaign I DMed for Frin, it would instead be characters such as the unidentified kraken that nearly sank her ship, the half-draconic pirate captain Rassan al-Harid, the vampire necromancer Nerachadni, the cultist leader monk that led an ambush later in Calimshan, Elashni the aranea hermit, the four wereboars that picked a fight with them somewhere (I don't have a map open right now!), the people she fought in the final session of the dreamscape arc, or the drider palemaster that actually managed to kill one of her companions. All of them had stat blocks considerably more potent than the other random mooks the party fought (usually offscreen), all of them presented a clear and credible threat to the survival of the whole party, and all of them rewarding, if not in loot, then in RP.

In the recent yuan-ti events, it would be the black dragon whose name I forgot, or the yuan-ti broodmothers. Ghost's "wandering hezrou" test also sort of counts, in that it was a lot deadlier than the other things you could find on the maps the hezrou visited. Sort of.

2. Can monsters have unusual immunities granted via items that are canon, even if players cannot obtain these items due to OOC rules?

Maybe, if they're canon. However, some of those items may also exist in the stores and loot tables, but have been deliberately nerfed to reduce the world's magic level or something. Periapts of health, for example, are supposed to provide blanket immunity to disease, if I remember correctly, but ours just provide boosts to saving throws.

Generally, I would argue against giving them items of a power level that surpasses the best the players can get. It makes one wonder why the PCs never bother to loot them off the bosses' corpses.