bliznik: Funny, I'm the opposite of you and play as a Fighter. Mainly b/c I find Geoffrey a rather boring character. I think the other characters are more interesting later on the series, but I found Geoffrey much more two-dimensional, and therefore don't really like him in the party.
The problem is that the game was not kind to the Fighter class. Basically, this class has these issues:
* You get no MP. This is, perhaps, reasonable, if the class is otherwise good (as it typically is in other RPGs), but unfortunately, it isn't for other reasons.
* You don't get any magic weapons other than the Mystic Sword. Seeing as non-magic weapons apparently don't work in the Abyss, this means that you're stuck with the Mystic Sword in the Abyss.
* Worth noting that this locks the Fighter out of using the strongest ranged weapons, and even worse, locks them out of being able to use any ranged weapons, at all, in the Abyss. Seeing as how magic isn't even an option, either, this makes this class easily the second worst, and in the Abyss, is actually tied with Shepherd for being the worst.
* Unlike Shepherd, which seems to be intentionally terrible, it feels like Fighter ought to have at least been decent, but sadly that is not the case in this game.
For the record, the NES version did somewhat address these issues:
* The Avatar gets 99 MP on reaching avatarhood, so even if you're a Fighter (or Shepherd), you get 99 MP for the Abyss. (It's a good thing, because the NES version expects you to do the Abyss alone, and I'm not sure if it would be possible without magic, even if it's the easier NES version of the Abyss.)
* All ranged weapons work in the Abyss, so the X-Bow, even if not as good as what other classes get, is still usable. Furthermore, you can equip it and the Mystic Sword at the same time, and the game will automatically use the appropriate weapon.
* There's a Fighter exclusive weapon in the NES version, the +2 Axe. Unfortunately, it's only melee, so long-term it's only useful if you have Geoff (his name was shortened) as a companion.
Britannia47: Again, sometimes the "Down" spell does not work although I am higher than eigth level. No explanation though, just "failed". I have prepared 99 ot them and magic points are there otherwise the game would state it instead of just saying "failed". Had to find a ladder in those cases.
bliznik: It's very possible that there's a wall directly below you, so it "failed" to prevent you from teleporting into a wall and insta-killing yourself. If it fails, try restoring and then moving one tile in a direction and trying again.
Don't forget that you can't teleport into a room.
Also, there's no mechanic to kill you if you somehow manage to teleport into solid rock. Rather, if you somehow manage to do this, the behavior I would expect is as follows:
* If there is an empty square next to you, you can move into that square.
* If you are in a room, and on the edge of the room, you can move out of the room in that direction. Do, however, note that if the rest of your party can't reach that particular exit, then you are trapped in the room and can only get out by killing everyone; if you are unable to do that, it's a softlock.
Incidentally, I try to avoid using the Up and Down spells myself, except for leaving the dungeon (Up on level 1, or in Ultima 5 Down on level 8.) Might use it to bypass the bug in Hythloth, though. (But who bothers to trek all the way through Hythloth, anyway?)
Worth noting that the NES version of Ultima 4 does not include those two spells.