So this Guide is about character classes and party composition in the Eye of the Beholder games. While I'm not an expert in the games itself, I've grown up with the rules and understand them quite well. I've also played 1 far more than 2 and 3, which shouldn't affect my judgement, but keep in mind that there could always be some unforseen consequences.
First of all, there's some classes and races which are increadably weak in EOB in comparison to the other AD&D games, which are gnomes, because the prime advantage of gnomes is to play illusionist, which aren't in the game, there's not even a gnome mage. Next is the fighter as the advantage of the fighter is his specialisation on weapons, which makes him "better" than the Paladin or Ranger, however, this isn't implemented in EOB, so Rangers and Paladins are objectively better as they can do everything a Fighter can and still have their unique abilities. Last of is the Mage, for a more obscure reason. One major drawback is his low hitpoints, as there are some effects, usually traps that affect all party members and it also provides problems when flanked. Next is that his spells are not very good. His best spell would be invisibility as making the front row invisible should make a nice tank upgrade, right? Thing is, if the front row is invisible, the enemy just hit's the second row as he finds no targets in the first, it's kind of a glitch. Also the mage doesn't get bonus spells thanks to high intelligence as in other AD&D titles, so yeah, he's pretty useless.
Aside from all that there are a lot of weak choices for race/class combinations, but I will go over the good ones, instead of the bad ones. Keep in mind that you can always almost instantly shift the position of the teammates, I even went so far as to use a macro (shift+f1,shift+f3,shift+f2,shift+f4), which switches the first and second row. So usually the first row are tanks, the second are damagedealers, which I quickly switch out with the first row, then switch back, before the enemy hits. The third row are supporters and/or ranged attackers.
+ Highest levelcap
+ Passive defence buffs for himself
+ Passive defence buff for the entire party
+ Fighterlike high hitpoints, defence and attack
+ Minor heal ability
- no racial advantage until very late in the games
- doesn't tolerate evil characters and bahavior, such as looting graves in EOB2.
So the Paladin is a pretty solid choice, in fact arguably the best one for the front row. His passives are better than most racial advantages, so the human drawback is negated. He's a like a fighter, just better. I highly recommend a Paladin.
+ Highest levelcap, which is important for hitchance
+ Good defence
+ Useful, but not essecial early turn undead
+ Acceptable hitchance
- Only good in front row
- Very restrictive weapon selection
- no racial advantage unitl very late in the games
- lacks 1 slot.
Having a cleric in the party is pretty much mandatory, now he doesn't need to be a pure cleric, but having no cleric screws you over big time. This human version retains an acceptable hitchance as the thac0 is lowered by 2 at level 19, while other races can only reach level 18. However aside from that, there are no relevant passives he benefits from. Also in the back row he can only throw rocks, which is weak, so he needs to be in front row, where he needs his symbol to cast spells, a weapon and a shield, but he has only two slots, so you usually stash the holy symbol away and let him only cast spells in between battles. However all in all, a human cleric is pretty solid, turn undead and flame blade are useful early on, until you find the mace +3.
+ Highest hitchance
+ Best damagedealer in the game
+ Good makeshift fighter
+ Capabale in every position
- lower hitpoints than non-elves
- can't be ressurected by "raise dead"
- picking the shortsword+3 in EOB is essential.
Alright, so the elf Rangers primary advantage is to have a weapon in each hand - that is usually a shortsword in the offhand. While others can do this as well, the Ranger suffers no penalty as long as he wears leather armor and on top of that as long as both weapons are swords, he benefits from his elven passive inreased hitchance which is honestly quite huge. You can also clad him in armor and put let him tank or give him a bow and put im in the backrow, but he truely shines with a weapon in each hand. Now shortswords for his offhand are a rare commodity. The basic version is only availible as a starting weapon and there's only one magical shortsword in EOB1, however picking that means you forego a good ring for mages and a good defensive item as you have to choose between the three.
If you are just playing EOB1, always pick an elven ranger instead of any mage. If you're going for all three games, that choice becomes more debatable with every iteration, especially in EOB3 when polearms are able to attack from second row.
+ Acceptable hitchance
+ Acceptable hitpoints
+ Acceptable makeshift character in any row
+ Decent archer
+ Can cast spells
- Armor conflicts with spellcasting
This elven fighter/mage is a suprisingly good choice for almost any party composition. While I consider a pure mage and a pure fighter to be pretty useless, this combination is actually good. It doesn't suffer from the mage's low hitpoints and hitchance, while beeing able to use spells and mageitems. Now spells aren't essential to EOB1, but you might want to start with this one. The reason is the scrolls, now you can take all scrolls with you and let them be learned by the npc mage in EOB2, however, you either won't transfer him to 3, thus the spells are lost or you transfer him and forego a character whichs stat you might have maxed out during character creation.
+ Good hitchance
+ Improved weapon selecetion over regular cleric
+ Excellent damage dealer due to flame blade spell
- Still a compromise between Ranger and Cleric
- lacks 2 slots
Now while I would say that a Fighter/Mage is better than a fighter and a mage, with the Ranger Cleric the compromise is more noticeable. The gain over the cleric in hitchance and hitpoints isn't huge. However the combination of the skills of cleric and ranger make him a powerhouse. You can equip a holy symbol in the primary hand, then cast flame blade to make it appear in the offhand, then you equip any weapon in the primary hand and you have a character that deals a lot of damage, since flameblade is very powerfull and availible early on. The downside is however, that once the flameblade expires, you need to repeat the process and keep a shortsword availible in case you run out of spells. So only pick this class if you have one character that has a surplus slot, so you can do quickly switch the holy symbol with a weapon, without accessing the inventory. However, since you use flameblades as offhand weapons you can and should skip on the shortsword +3 in EOB1 and go for the defence bracers or the ring of wizardry. Offsetting the downsides of the Ranger and the Cleric, this one is a pretty good choice.
+ Can pick locks.
+ Capable of solid attacks in comparison with other races' thieves.
+ Surplus slot.
- Lacking in attack, defence and spells.
- Kind of redundant, due to good NPC in EOB1
Sigh, okay the thief is for the most part purely decorative. In EOB1 there's only a handful of locks to pick and even lockpicks are rare. However, having a thief in the party get's more important in the later games and becomes mandatory in EOB3. In EOB1 you'll find an NPC, Tod Uphill, who has increadibly good stats for a thief. So you might as well transfer him to the later games, making a custom made and statmaxed thief a poor choice for EOB1. However you can still do this, if you are certain you want to transfer him to later games and the additional lockpick is a nice bonus in case Tod's one breaks. Thief's should have a sneak attack damage bonus, but I'm pretty sure that's not implemented in EOB1 - or at least not in a reliable fashion. So yeah at some point you need to weaken your party with a thief, the question is just how you approach that problem and a halfling thief is a solid solution.
+ Niche choice
+ Only way to create a cleric/thief
+ Cleric and Thief have complement each other well.
+ Can pick locks
- Lacks 1 point of wisdom (and dexterity)
- has harsh level restrictions
First things first, there's a lot not to like about this combination. Gnomes make weak clerics, due to their low wisdom and can only reach level 12. The thief part foregoes the +1 dex of other races, thus making it effectively reduced as well, but not as harsh as the cleric counterpart. Gnome thiefs max at level 16, which is acceptable since it's multiclassed anyway. However the main advantage is that the cleric benefits the thief with an wider variety of armor he can use and the thieftpart makes more weapons availible. Hitchance and hitpoints aren't great though. All in all certainly the best way to play a gnome in EOB, but not very powerful in itself. However, this might still be a good pick in certain party compositions. Since the two mandatory classes are combined into one whithout sacrificing too much there's room for one more specialist in the party, which can make up for the cleric/thief's weakness. Actually, if you would just want to play EOB1, this is a pick I can recommend.
+ Niche choice
+ Nice passive racial buffs
+ Can pick locks
- Decresed defence due to lower dexterity.
So again, this is a bit of a tricky one. A thief and a fighter/mage is certainly a better choice than a mage and a fighter/thief, but still one might prefer a fighter/thief over a pure thief as lockpicking is rarely used. The lowered dexterity isn't great, but the levelcaps are highest. All in all, you can use this one, but again it's not great, but a viable thief pick.