Questions about Incorporeal

[Gunny43]

Hey guys, I had a quick question about incorporeal creatures. There are going to be some in an upcoming session in my campaign, but the rules threw me for a loop on the first few read-throughs.

"An incorporeal creature has no physical body. It can be harmed only by other incorporeal creatures, magic weapons or creatures that strike as magic weapons, and spells, spell-like abilities, or supernatural abilities. It is immune to all nonmagical attack forms. Even when hit by spells or magic weapons, it takes only half damage from a corporeal source (except for channel energy). Although it is not a magical attack, holy water can affect incorporeal undead. Corporeal spells and effects that do not cause damage only have a 50% chance of affecting an incorporeal creature. Force spells and effects, such as from a magic missile, affect an incorporeal creature normally."

I want to make sure I have this right. If a barbarian is wielding a +1 greataxe and swings on the ghost, he deals half damage; if the archer in the back with a mundane bow tries to shoot it he does nothing; but if the priest in the back slaps the ghost across the face with channeled energy (or with a Ghost Touch mace) he deals full damage.

Additionally, the wizard standing next to the archer trying to cast "Bestow Curse" or some other nonsense on the ghost only has a 50% chance of having it work. But if they had a friendly ghost on their side, it could use whatever it had, from a random pointy stick to a delayed-blast fireball, without any problems on the enemy incorporeal?

Also, if the incorporeal enemies wanted to set up an ambush, could they hide inside the walls? Or is the theory behind incorporeal enemies that they're less the traditional "you cant hit me im an ethereal spoopy ghost" and more "my physical makeup is similar to mist or smoke", in which case could they just sorta shimmy up next to a wall and wait?

And last but not least, the incorporeal creature can affect all four of them normally without a problem (or even the friendly ghost if he gets mad at the traitor)? The creature in question is a shadow, and I only ask because I was thinking about switching it up and using a Wolf shadow instead of a normal shadow and one of its abilities states it has to turn corporeal to use its bite/trip.

[Tyrant Lizard King]

You got it from what I can see here as far as how damage is resolved.

For your ambush question;

An incorporeal creature can enter or pass through solid objects, but must remain adjacent to the object’s exterior, and so cannot pass entirely through an object whose space is larger than its own. It can sense the presence of creatures or objects within a square adjacent to its current location, but enemies have total concealment (50% miss chance) from an incorporeal creature that is inside an object. In order to see beyond the object it is in and attack normally, the incorporeal creature must emerge. An incorporeal creature inside an object has total cover, but when it attacks a creature outside the object it only has cover, so a creature outside with a readied action could strike at it as it attacks. An incorporeal creature cannot pass through a force effect.

Also, don't forget that they would have Undead Traits as well. So if you managed to use bestow curse and chose -6 to STR, nothing would happen.

Undead Traits (Ex)

Undead are immune to death effects, disease, mind-affecting effects (charms, compulsions, morale effects, phantasms, and patterns), paralysis, poison, sleep, stun, and any effect that requires a Fortitude save (unless the effect also works on objects or is harmless). Undead are not subject to ability drain, energy drain, or nonlethal damage. Undead are immune to damage or penalties to their physical ability scores (Strength, Dexterity, and Constitution), as well as to fatigue and exhaustion effects. Undead are not at risk of death from massive damage.

Force spells like Magic Missile deal normal damage and Incorporeal cannot pass through force effects like Wall of Force.