The Spiritualist is sort of like the Summoner, except not.
The Spiritualist is a pet class, like the Summoner. That means they have a buddy that, instead of being some strange outsider, is a dead person. This dead person represents a certain concept, like Wrath, Pride, Greed, Hatred, or Lust (giggity). More on this later.
The Spiritualist has 3/4ths BAB and 6-level spellcasting, along with light armor and simple weapon proficiency. However, their spell list is more focused around Necromancy, instead of Conjuration, like a Summoner.
What really makes the Spiritualist different is the fact that, well, you've got a ghost buddy hanging around that wants its unfinished business finished. This ghost buddy has a number of forms- it can take up residence in your head, become ectoplasmic, or even become incorporeal, which is powerful at low levels. As well, the Spiritualist can call upon its spirit buddy to create an ectoplasmic/incorporeal body shell around it. By being near the spirit, the Spiritualist also gets a solid bonus on all of its saving throws AND a bonus to armor class.
When the Spirit is inside the Spiritualist's head (which doubles as keeping it safe and sound), though, it grants a bonus feat and a bonus to a number of skills. At later levels, the Spiritualist gets this bonus even when their spirit is outside of their head.
All in all, it's a solid class. Not as powerful as a Wizard, but it still gets the advantage of what amounts to an extra set of turns and 6-level spell casting. It also makes for great roleplaying, as all manner of story opportunities can come up when you have a ghost living in your head.
|The Classes of Pathfinder|
|Core Classes:|| Barbarian - Bard - Cleric - Druid - Fighter - Monk |
Paladin - Ranger - Rogue - Sorcerer - Wizard
| Alchemist - Antipaladin - Cavalier |
Inquisitor - Oracle - Summoner - Witch
| Arcanist - Bloodrager - Brawler - Hunter - Investigator |
Shaman - Skald - Slayer - Swashbuckler - Warpriest
| Kineticist - Medium - Mesmerist |
Occultist - Psychic - Spiritualist
|Ultimate X:||Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante|