Ghost Manifestation Abilities

[An Enemy Spy]

In the Monster Manual it says ghosts have one to three manifestation abilities they can use in combat, but there's no instructions on how to determine how many they have. Is it just purely up to the DM's discretion when making a ghost how many to give it?

[Tzardok]

Some sourcebooks may have specialized ghosts with a specific number of abilities, and Ravenloft books give more stringent rules with ranks and the number of abilities depending on that, but in general the DM decides how many.

[DivineOnTheMind]

Totally discretionary.

There's the Ghost Template Class from the old "Savage Progression" articles that rations out either one of {Corrupting Touch, Frightful Moan, Telekinesis} and one of {Corrupting Gaze, Draining Touch, Horrific Appearance, Malevolence} or all three from the first list.

[icefractal]

Personally speaking, in 3E:
For NPC Ghosts I rolled 1d3. For PCs, they always got three, because +5 LA is a lot.

In PF1, it's based on total CR. And also the LA (CR, really, but that's what's used) is a much more appealing +2.