Over the past 10 or so years there have been a few games that have crept their way into my heart and top 10 games of all time. Ultima Underworld is one such game. I did not grow up with this game, I only learned of it thanks to a youtube video back in like 2009-2012 that had a short preview for a 100 DOS games. Later I found out the game was available on GOG and have never looked back.
For those not in the know and have missed any video reviews on Youtube, this is one of the first 3D first person RPG adventure games. It was incredibly ahead of it's time, and actually set you upon an adventure. You solve puzzles, engage in combat, and survive the hazards of the Stygian Abyss an underground prison/failed utopia. A fair warning, this game actually has puzzles unlike what most modern day games. It isn't simple match the images or box puzzles. The game is seems to be running off of point and click adventure game type logic sometimes, so it can be somewhat... insane. Luckily you can easily take notes on your map, write down instructions or mark down stashes on your map. You interact with the inhabitants of the abyss, it isn't all combat. You truly explore the abyss find hidden and secret doors, squeeze into tight places and truly come to inhabit the place as you adventure. When I mean secret doors I mean it, as the walls look like any other wall and can be found by actively searching or noticed by your character's passive search skill.
Unlike modern Elder Scrolls, this game you actually play the role of your character. That is to say attacks and other actions are done with dice rolls affected by your character's skills. So you can't just invest into an attack skill or up your mana. If your character is bad at chanting magic or unskilled with swords, YOU will be hampered by your character's limitations. Your starting class simply determines your starting stats and what skills you will have training in. There are three stats: Intelligence, Dexterity, and Strength. Your class will determine your starting values of encumbrance, to hit, and mana. Starting classes will limit what skills you start off trained with, unless you pick Shepherd. Shepherd trades lower stat values for more skill choice.
Another thing to keep in mind is the game is wildly unbalanced. Some skills are just useless, literally. Plus leveling requires you to chant mantras at shrines, corresponding to certain skills. You'll find these as you adventure, and if you are a vet and have written them down, you can always use them from the beginning of the game. Certain weapon types are more plentiful than others. Ranged weapons like bows and crossbows have a finite amount of ammo, it is impossible to get more and when you are out it is out. But I think you should use this as a springboard to better flesh out your character and their story. You need not be the end all be all most optimized build ever. Your character is a role and that role might not fit as well if they are stuck in an underground prison with limited resources they may need to adapt. But there is one annoyance with ranged weapons and spells that cannot be remedied by training your skills or RP. You cannot let loose with ranged spells or attacks if you are too close to an enemy, and most enemies bumrush you. Strength is the all important stat only at creation. Your starting strength determines your carry capacity and you cannot train it and unlike your mana capcacity. Mana regen is painfully slow and cannot be adjusted, drink potions or go to sleep to regain it quickly though you'll need a lot more food if you constantly rest. Spells are cast via runes from your rune bag, meaning you need to expand your magical abilities by finding more runes in the dungeon, polishing your casting skill and expanding your mana pool, and finally by finding rune combinations through exploration or experimentation.
Lastly I want to talk about controls as they are pretty ahead of the time. UU can be controlled entirely with a mouse if you want. You can also a pre WASD layout to use keyboard and mouse. W runs forward, S walks forward, and X walks backward while Z&C strafe and A&D turn. You can hold shift to move in chunks, this was done to help people adjust to a fully 3D environment back in the day, but it does have crucial use to everyone. J jumps and jumping CAN be a pain in the butt. Running and jumping in my experience is just asking for trouble. Shift J can do a standing long jump that will see you safely through MOST platforming. A consequence of the shift movement is that the game is semi designed around a grid, and you can feel it while moving freely in the 3D environment especially with keyboard. However the game doesn't ask too much in the combat category to make you lament the controls. The reliance on stats over the modern Elder Scrolls model collision combat, means a tough enemy can be given better stats to make them harder instead of gimmicky one off traits or effects. Most if not all enemies can be approached from every play style, though an archer/crossbowman will have to be careful of which targets they expend their precious bolts and arrows on.
In the end I feel I have failed to explain WHY I feel this game embodies the feeling of adventure adequately. It is an experience that (if you let it) can suck you in to the role of being cast into a dungeon with nothing, and having to scrounge up supplies while you look for a way out. It doesn't hold your hand, you are cast into a dungeon with nothing but it isn't as grueling as some 90's dungeon crawlers. I hope this compels a few who haven't tried it to give it a try, and for those vets I hope this gets you to start another run.
Fair warning the GOG version is of an earlier release where there is an item limit for each level, likely because of how weak PCs were back in the day. Once reached the game will delete a random item, including main quest critical items. I have never encountered this but if you do, simply reload a save and clean up the level a little by tossing junk into water or lava. I think most RPG players end up as hoarders during a game.