Claymore! is a roleplaying game that utilizes a single combined point pool for all character generation steps. For example, each Race, Ability, and Skill is purchased with points from the same pool. Character generation is very complicated and involved (and involves several scores that are not thereafter referenced in the rules). Race selection has a significant impact on subsequent character development. There are twelve Races, namely: Blue Elf, Catling, Dogling, Dwarf, Elf, Gnome, Halfing, Human, Nephilim, Ogre, Pixie/Sprite, and Xenophobe. Some races have a negative point cost, thus returning points to the common pool. Half races of any combination are optional. Height, weight, appearance, and age are generated randomly. Social Status also is randomly determine and subsequently determines starting money. Curiously, the character then selects an Myers–Briggs Type Indicator during personality determination (personality determination is quite complex). Characters also select Blessings and Tests, which are used during campaign play. Characters select one or more Skills from a lengthy list. The character is then equipped.
For spellcasting characters, an equally detailed but separate process is followed to determine magical power, power pool points, and specific magical abilities. Psionics are treated as a magic system. The spellcaster generation also results in a starting spell list.
The remainder of the core rules is devoted to Combat and opposed skill resolution. Combat, played on a hex grid, requires players to perform "action declarations" prior to each round; this locks in a specific action. The round then proceeds through two phases (movement, combat) with characters acting in initiative or surprise order. Combat supports several "Extreme Dice Roll" results, ranging from Fumbles (broken weapons, etc.) to Critical Hits (see below). Several types of attacks are supported, such as "Careful Aim", "Disarm Attack", and "Charging", etc. A variety of special combat actions also are detailed (Tackle, Grappe, Sweep, Throw Heavy Object, etc.).
The remainder of the core rules provides Technology options and a bestiary, and a collection of tables. A separate six-page document lists numerous skills, many of which are not included in the core book. The game also incorporates by reference the Critical Hit tables from Iron Crown Enterprises' Rolemaster System.