There's no recruitable mage NPC in this game. If you want to cast arcane spells in this game, you'll need to bring a mage along. Multiclass of course will be fine.

I never finished Stone Prophet, but I imported my fighter and cleric from a completed Strahd's Possession game. While having a mage is certainly handy, I never found it that pressing compared to having a cleric who can cure poison and can summon food and water. Perhaps I did not get far enough (completed the Obelisk) to demand a mage of some sort, but if I had to have a mage, I would recommend a mage/cleric. I always found it suspicious that the game made practically every NPC a cleric or a multiclass cleric hybrid.

Of course, considering the bugs in Strahd's Possession, the absence of an NPC mage could be an oversight, too. :D

Started Stone Prophet with a fresh party. I had a Human Mage (better starting gear than other races) and a Half-elven Fighter/Mage/Cleric (better starting gear than the Mage/Cleric). I added the Wemic and the Cleric/Ranger and I have almost finished the obelisk and my main problem is finding not enough high level mage scrolls. (Strahd's possession was more generous with starting spells)

Having lots of ranged firepower makes dealing with the Manscorpions a lot easier.

You don't need a mage, but one does come in handy. It seemed odd to me, though, that an RPG would omit a whole archetype when it comes to it's recruitable NPCs.

From what I remember, I did do well without one. I am replaying Strahd's Possession and I won't try again until I deal with Strahd and import my party. I DO remember that starting with a Cleric made the first stages much easier than they could be with a fresh party or the default quick start characters.

Are you talking about Strahd's Possession? There you would want a cleric to turn the golems, that the game throws at you. Without one you're in for a world of pain. Also healing and negative plane protection. A cleric is probably the most important class in this game, considering how many undead monsters you encounter in there, and it takes a while, till you can recruit a cleric NPC. The quick start party consists of an elven fighter/mage and a dwarven fighter/cleric. Perfectly valid.

In the Stone Prophet you have access to a ranger/cleric NPC right in the beginning of the game. The quick start party consists of a half-elven cleric/ranger and an elven fighter/mage. Also perfectly valid.

I know Strahd's Possession like the back of my hand. :) I use a single class fighter and a cleric until I can pick up Velika and Glorianna for arcane backup. Add the Dagger of Throwing, the Rod of Smiting and the Axe of Throwing you pick up later in the game and you have a total package both up close and at range. A PC cleric is pretty much mandatory. Mischa, the NPC cleric, isn't available until after one of the nastier segments in the game (the Cemetery and the Elven Tomb). Imgarde is a crutch character for the Ilvis dungeon because of the bone golems and she is gone after that dungeon. I ALWAYS have Aid and Neg. Plane Prot. active. Turning golems is kind of a crapshoot. The quick start party characters are acceptable, but I always felt that they were not as great as they could be. I am trying them out and, to be blunt, I am not that impressed with them. I will wait until after I finish Strahd's Possession again to import my fighter and cleric.

Too bad the rod of smiting doesn't transfer into the Stone Prophet. So don't throw away your warhammer +2. ;-)

I take this back. I had forgotten how laughably effective turning Zombie Golems really is. It is hilarious watching the nastiest enemy next to the treants and Strahd, himself, dance in circles while you kill them unopposed. :D