[Obscure Games] Rolemaster

 Originally published as an alternative combat system for Dungeons & Dragons, followed up by an alternative magic system and finally an alternative character creation system, Rolemaster began as the individual books Arms Law and its follow-up Claw Law, Spell Law, and finally finished up in its basic form with Character Law and the GM-focused book Campaign Law. Shortly after, though, methods that helped distinguish the game on its own were published as optional rules set out in a series of Rolemaster Companions, with seven of those in the main series and several more focused on specific topics (like Elemental Companion or Oriental Companion; the latter, like AD&D's Oriental Adventures, came out before "Asian" was generally understood to be the preferred adjective for describing Asian nations and cultures, even though it seems obvious now). To my way of thinking, the first two Companions are essential for the game, with the first including the "Smoothed Stat Bonus" table and the second offering a complete listing of skills and their effects in the game. There are a number of other optional rules in the various Companions that some may like, such as alternate initiative and turn sequence systems, additional ways to use magic, more developed systems for mounted combat, and so on. All of the Companions also include new character classes, which are usually at least of interest (I'm personally a fan of Rolemaster Companion 2's Dervish class).

The game is really very simple in concept, with almost all actions resolved by rolling percentile dice, adding a bonus based mostly on skill, and either hoping for a result of 101+ or comparing the result to a table to derive a degree of effect. The dice roll, in most cases, is "open-ended", which means that a dice roll of 96 to 100 allows the player to roll again and add the result, potentially rolling more times if more results of 96 to 100 are scored (and a similar downward result subtracting additional dice rolls can begin on a roll of 01 to 05, continuing to subtract more rolls if 96 to 100 results are obtained on the negative dice, though occasionally rolls are defined as "open-ended high" which precludes such negative results). In Arms Law/Claw Law, the table for each different weapon is divided into columns representing different armor types and the result of the dice roll is cross-indexed to get a number of "concussion hits" to be applied to the target's hit points and, often, a letter result for a "critical", which is rolled by a percentile roll (usually unmodified) on a table to derive a more detailed injury result. Such "crit tables" are defined by the injury type and the letter degree, so that a critical result might be described a "B Slash", an "A Crushing", or a "C Burning" to indicate which specific critical result table and which column to reference. Most characters involved in combat will be affected by crits rather than accumulated concussion hits, especially as they move beyond the lowest levels.

Other than simple attack rolls, actions are usually defined as "Movement/Maneuvers" or "Static Actions", and rolled similarly by comparing an open-ended roll, modified by skill in most cases, to a column representing the difficulty of the action on a table found in Character Law.

The character creation rules give ten attributes to each character, rolled on normal percentile dice, rather than open-ended ones. These attributes provide a modifier, and in some cases a number of "development points" or other benefits. The player takes thee total development points and spends them on skills which are given point costs that vary by character class. Further, the number of skill ranks that can be purchased at a time varies by character class, so that a Fighter can buy two ranks in most weapon types at each level, while magic-using classes can't buy more than one rank, and the situation is basically reversed when attempting to learn spell lists, so that magic-using classes can buy as many ranks in a spell list as they can afford, but Fighters are limited to only one rank in a spell list "Pick" per level, and that one for a high cost in development points. Skill ranks and attribute bonuses, plus some other benefits, are added together to give a total skill bonus to use when attempting to use a skill. For spell list "Picks", this allows a roll during the "level-up" process to see if the character acquires the spells of that "Pick" type from that list. This is usually 5 or 10 "levels" from the spell list. Casting a known spell costs spell points equal to the spell's "level". Some spell lists do not have spells of certain levels. The "Picks" that a character is allowed to attempt to learn vary depending on the specific spell list and its relation to the character's class, such as if it is a "Base" list for the class, "Open" or "Closed" in the category of spell use for the class (Essence, Channeling, or Mentalism), and so on, as well as if the character has any previous "Picks" from the spell list, such that a "C Pick" requires a previous "A Pick", a "D Pick" has a "B Pick" as prerequisite, and so on.

So, you can see that most of the game's complexity is actually front-loaded into the character creation and advancement process, contrary to its reputation. Some people find referencing the action charts to be onerous, but that seems a frivolous complaint to me.

After the core rule books, the game has some other supplementary books of value. Creatures & Treasures provides a good list of both foes and magic items. Personally, I only think the first one is worthwhile. War Law provides a mass combat system for the game, while Sea Law gives nautical rules and equipment, like ships and such. In addition, Space Master adapts the rules for SF games, with Armored Assault giving vehicle design and combat rules, while  Star Strike does the same for spacecraft. A setting book titled Dark Space offered a setting that mixed the SF and fantasy elements with some horror concepts.

In general, I don't think that the game deserves its reputation of being particularly complicated, though there is a certain amount of system mastery that is necessary to play characters of some types, with spell-using classes being more difficult to play than combat- or stealth-oriented ones. It certainly has a very particular flavor that is different than most other games.