How are the characters/plot in those games?

The characters are generic, they don't have any identity or history, there are no party banters. There are 3 races and in some encounters, having a specific race in the group plays some minor role but nothing really important. There isn't much role playing or decision making in the game. In avernum 3, which is quite open world, you are cast in the surface and have to save the world from some plagues. In one of them you have to destroy a cockroach factory:) And there are some interesting timed events, not saying more but if you aren't well prepared it may be game over. In avernum 5 you chase an assassin who is the leader of some rebels and at some point you can choose to join the rebels but it doesn't really change much to the game. Did I mention no thieving skills /class in the game? In most games the group you build for efficiency is a fighter with a two handed pole weapon, a tank with sword and shield or an archer, a mage and a priest who is not very useful offensively. You can have two mages or a mage/priest but not much variety in terms of classes /composition.

Thanks for the detailed reply! I have Avernum: Escape From the Pit and the Geneforge games, so I appreciate you letting me know what you thought of them. As an old-school CRPG lover, Spiderweb Software games have piqued my interest, though I've yet to try them.

One thing that might be worth noting:

In Avernum 1, 2, and 3, a mage/priest can actually work decently well; because it becomes more expensive to improve higher level skills, hybrids are actually a viable option. Sometimes, giving a character a little priest magic can come in handy, for example. Also, you can eventually get unlimited skill points in these games, though not until late, and in 1 and 2, quite expensive. (In 3, it requires a special recipe that is as difficult to acquire as an artifact.)

In Avernum: Escape from the Pit (and probably the Avernum 2 and 3 remakes), however, hybrids are not viable, as the points above do not apply. It's also worth mentioning that magic is apparently really good in these remakes, to the point where a 4-caster party (with enough weapon skills to get access to certain battle disciplines) might actually be optimal.

Avernum 4-6 have increasing skill costs like Avernum 1-3, but don't have infinite skill points. Some of your skill points will still come from consumables, so it can still make sense to have some characters use builds that demand more skill points than others.

By the way, one interesting fact about Avernum 1-3; the luck stat is actually useful. Each point of luck gives you a 5% chance to survive fatal blows, so at 19 luck, you have a 95% chance of surviving anything that would otherwise kill you. (The chance doesn't increase any further.) This, needless to say, can make you very difficult to kill, though it takes a lot of skill points to raise the stat that high.