The Nameless One only has three classes at his disposal and the most basic ones at that. Surprisingly, despite being human, he can’t dual-class, even though two of his teammates are multiclassed. Or well…he can’t do it legitimately, but there is a bug you can exploit to enable him to cast spells as a Fighter or a Thief. You may also wonder why he can’t become a Priest, but there’s an in-game reason for that. As has already been mentioned, TNO starts as a Fighter, but later encounters NPCs who will enable him to become a Mage or a Thief. This will restart him at level 1, but he’ll be able to revert to any class at will once he recruits Dak’kon and Annah. E.g. if he was a level 5 Fighter before becoming a Mage, he’ll revert to a level 5 Fighter. In any case, he will always retain the best THAC0 score of the three classes (which usually means Fighter). As his alignment is in a state of perpetual flux, it doesn’t restrict his choice of class.
Attribute allocation is a lot less annoying than in Baldur’s Gate, since you don’t actually have to ‘roll’ TNO. He starts with a 9 in every attribute and is given 21 points to distribute as you see fit, with one additional point per level after that (in his highest level class). However, due to the game’s heavy focus on dialogue, Wisdom, Intelligence and Charisma are the most important attributes, in that order. Everything else is secondary, and can be raised via items, conversation choices or equipment. There’s really only one optimal attribute distribution, give or take a couple of points, which may affect your choice of class.
Each class grants TNO a stat bonus at level 7 and 12, which reflects its individual strengths (e.g. an Intelligence bonus for a Mage). Two things to note here: if TNO gets the level 7 Fighter bonus, he won’t get another for hitting level 7 as a Thief or a Mage. Moreover, he can only get the level 12 bonus if he is the same class as at level 7. So say he hit level 7 as a Fighter, but then proceeded to level 12 as a Mage; instead of getting the level 12 Mage bonus, he’d get the level 7 one. In short, make sure to hit level 7 and 12 with the same class. A similar system applies to HP: every class has its own progression rate, but if TNO has already gained the requisite HP for a given level in one class, he’ll only gain 1HP if he hits that same level with another class. E.g. he gains 8HP as a Fighter at level 4, then switches to Thief; he’ll only gain 1HP per level until he hits level 5 as a Thief, at which point, he’ll start gaining HP at the normal Thief rate. Thus, the usual procedure involves being a Fighter until level 6, then switching to a different class to obtain its level 7 bonus, if you so desire, switching back to Fighter for levels 8 through 11, then back to your class of choice for level 12 and onwards.
Fighter: This is TNO’s default class and, as is usually the case, the most straightforward one: grab weapon, hit things. You could simply coast through the game as a Fighter from start to finish, but if you want to maximise EXP, you’ll want to switch to the other classes, at least temporarily. The Fighter is second in terms of levelling speed, has a 1d10 HP progression base up to level 10, and 3HP per level after that, but also the best Saving Throws. It also gains one point of THAC0 per level (although it can’t go lower than 1) and one weapon proficiency point every three levels. The Fighter can use any type of weapon, and if you allocate points to weapons that a Thief or Mage can also use, you’ll retain them if TNO switches classes. However, there’s a slight catch: you can’t allocate them straight off the bat: TNO needs to be trained in his weapon of choice (cue Christopher Walken dancing) by a trainer NPC first. Moreover, the ability to put five points into one weapon type (Grand Mastery) is only granted at level 12. Be that as it may, since TNO is always at the front of the party formation, being a Fighter makes sense from a tactical standpoint. It also allows him to use some unique weapons. Strength is the most important attribute, but Dexterity also helps with accuracy and defence. However, due to the necessity of focusing on Wisdom, Intelligence and Charisma to get the most out of the game, expect your TNO to be subpar until you have points to spare for Strength and Dexterity (or until you find good equipment).
Thief: This is usually the first class that TNO will be able to switch to, and, frankly…it’s a waste of time. Being a Thief doesn’t grant him any glaring advantages, unlike Fighter or Mage. The main selling points of this class are its abilities–Stealth, Detect Traps, Pick Pockets and Open Doors–, but Annah can cover your needs in that department more than adequately. The Thief gains a THAC0 and damage bonus for every hit it lands while hidden, but this is the only combat perk it has to offer and a rather annoying one to consistently use. It has a 1d6 HP progression base up to level 10, and 2HP per level after that. It starts out with 40 skill points and gains 20 more every level, as well as one point of THAC0 every two levels (although it can’t go lower than 11). It’s also the fastest-levelling class of the three, but has the worst Saving Throws. In terms of weapons, it can use daggers, clubs and knuckles. Honestly, I would only switch to Thief to benefit from Annah’s training, which eventually allows you to improve her own skills. Other than that, both Fighter and Mage are far better options. Still, if you must, put points into Dexterity as soon as you can spare them.
Mage: Being a Mage in an oldschool RPG is an exercise in frustration. They only have a certain number of spell slots per spell level, which limits their casting abilities and forces them to rest frequently. The catch is that there are very few places in PST where you can rest safely. The other major drawback is that there are no ranged weapons in the game aside from Nordom’s crossbows and Ignus’ fireballs, which forces a Mage TNO to melee if he doesn’t want to waste spells on minor encounters. Moreover, TNO will always be placed at the front of the party formation, regardless of the configuration you choose, thus endangering him even further. The fact that the Mage has the lowest HP progression of the three classes (1d4 base until level 10, then 1HP per level afterwards) doesn’t help. It’s also the slowest class to level and only gains one point of THAC0 every three levels. It does, however, have better Saving Throws than the Thief. That being said, there are quite a few Mage-specific dialogue paths and events that result in hefty amounts of EXP and goodies. Moreover, TNO’s optimal attribute distribution does place a significant emphasis on Intelligence, which determines the amount of spells he can learn. All in all, I’d probably suggest Mage as TNO’s final class, although feel free to make him spend some time as a Fighter to improve his HP. Just as long as you hit levels 7 and 12 as a Mage.