Eye of the Beholder

Eye of the Beholder is a trilogy (or just a pair) of RPGs developed in the early nineties, the first two by Westwood Studios that would later be known from games such as Command & Conquer, and the third one by Strategic Simulations Inc., that also published all three games.

The games use a simplified version of the rules for Advanced Dungeons & Dragons 2nd edition, in the Forgotten Realms campaign setting.

All games are first-person, and feature an adventure party, between four to six members, going on quests and fighting evil. The first game has them hired by the lords of Waterdeep to investigate an evil residing under the city. It had an Absurdly Spacious Sewer, not just one but two ruins of lost civilizations beneath Waterdeep, and an infamous ending, where the player was treated a window of text before dumping them back to DOS (the Amiga version, however, added a proper ending cutscene). The second, generally thought to be the best of the series, involves the party checking out an ancient temple for Khelben "Blackstaff" Arunsun. It had more roleplaying content and much better ending.

The third game, assuming you're willing to acknowledge its existence, sends the player into the ruined city of Myth Drannor. It was not made by the original developers, and is generally considered a massive disappointment.

A Spiritual Successor, Lands of Lore, was created by Westwood in lieu of a third Eye of the Beholder after the split with SSI over creative differences.

A remake of the first game was released for the Super Nintendo, and later for the Game Boy Advance. It was also ported to Mega CD, with music composed by Yuzo Koshiro. Note that this remake diverges quite a lot from the original game, both in game mechanics and in that it adds sub-boss enemies.

The Eye of the Beholder series provides examples of the following tropes:

 * Absurdly Spacious Sewer
 * Anticlimax Boss: The Big Bads of both games are relatively easy to handle because of level design. The first game's big bad becomes much more climatic if you defeat him properly with the quest item Wand of Silvias.
 * Arbitrary Headcount Limit: You start the game with 4 characters, even when importing to the sequels. You may get upto 6. The second game also has an NPC that runs off, but he won't do it if you reduce your party size after recruiting him.
 * Bag of Spilling: Averted (see Old Save Bonus below).
 * Disc One Nuke: The magic dagger Guinsoo, obtainable in the very first level of the original game. However, you may never figure out how to get it... Well, it's only a +4 dagger, hardly a nuke.
 * Disintegrator Ray: The Disintegration spell, and the Beholders' most deadly attack (although, see Normally I Would Be Dead Now below).
 * Dummied Out: There is a removed area in the very first level of the first game, containing a portal and an unused portal key.
 * Faux First Person 3D
 * Fireballs: Not only the spell itself, but there's also plenty of traps that would launch a Fireball at the unlucky victim.
 * Giant Mook: EotB2 places giants within one of the dungeon levels. They are crawling within the 10' cube, and are able to hit three characters in a single punch.
 * The Goomba: The kobolds in EotB1.
 * Moon Logic Puzzle: Every dungeon level of the first game has a special secret that you can discover if you perform a specific sequence of actions on that level (the first level's is the aforementioned Disc One Nuke)... and the game only gives very obtuse hints about what those actions are. For example, put rations in the closet labeled "pantry", or eggs in the room labeled "nest".
 * Interchangeable Antimatter Keys: The "antimatter" part is handled by the keys being jammed in the locks. The 3rd game actually averts this in several spots.
 * Made of Explodium
 * EotB1: Explosives Runes, but only in the remakes.
 * EotB2: Gas spores.
 * Master of Unlocking
 * Meaningful Name: Dran Draggore.
 * Mooks Ate My Equipment
 * The rust monsters in EotB1 will eat any metal item.
 * The gelatinous cubes in EotB2 can also destroy items on a hit.
 * The black puddings in EotB3 will eat your weapons if you attack them in melee.
 * Normally I Would Be Dead Now: In EotB1, Xanathar's Disintegrator Ray, by AD&D rules, should kill instantly, but instead inflicts exactly 100 HP of damage. No One Should Survive That, right? Well, except if you have a high-level dwarf fighter with 19 in Constitution and the maximum possible on each roll (thanks to Save Scumming and Level Grinding)... that character can perfectly have more than 100 HP by the end.
 * Old Save Bonus: The sequel can be started with the party from the first game -- along with all their equipment, containing a significant amount of weapons and armor that outclass everything available in the second game. If you play it right, you end up with at least three +5 weapons and a dozen +5 darts, whereas the best weapon available late in the sequel is only +4.
 * Our Dwarves Are All the Same: Most of the NPCs that can join you in the first game are dwarves. All are fighters with An Axe to Grind and preferring heavy armor, practically identical except in stats. The dwarves that can be seen in large amounts in their camp are, other than a single exception, literally all the same: your basic bearded, heavily-armoured, axe-wielding type.
 * Pressure Plate: Full of them.
 * Puzzle Boss: Xanathar the beholder can be easily defeated by . He can be killed by regular means as well, though.
 * Save Scumming: Quite useful, especially if you save just before a character gain a level (and thus can "re-roll" the Hit Points for a better result).
 * Scaled Up / Turns Red:
 * Schmuck Bait: If you're warned to not enter the room full of awesome magical items... you shouldn't.
 * Take Your Time
 * Turn Undead: A power for the cleric or the paladin, along with the D&D rules. In EotB1, it is an automatic function, as long as the character is holding a holy symbol. Starting with EotB2, it becomes an action like any spell-casting, though not limited in use.
 * Universal Poison
 * Voice With an Internet Connection: Khelben Blackstaff, in the second game. Subverted once,
 * Warp Zone: The magic portals, especially the room with five of them in EotB1.
 * A Winner Is You: The MS-DOS version of the first game is notorious for its anticlimactic ending.
 * Wizard Needs Food Badly: Not so much of an issue though, as the game gives you more than enough rations to last until your cleric can learn a very useful "Create Food" spell, that instantly fills the entire party's hunger bars. The first game actually contains enough food to make it through without the Create Food spell -- although adventuring without a cleric is a bad idea for other reasons.