About Mythras and Mythras Imperative

Mythras is¹ the most refined version of the BRP²/D100 family of RPGs. With a lineage from RuneQuest, Call of Cthulhu, Stormbringer, etc., Mythras is a flexible RPG toolkit that’s been adapted to settings from ancient Rome, Britain, Babylon, and more, to space opera and superheroes (it’s even been adapted to everyone’s favorite old school dungeon crawling setting). Multiple magic/powers systems and gritty, dangerous combat are hallmarks of D100 RPGs, and Mythras has some of the best on offer.

Mythras Imperative is an ORC-licensed, slimmed down version of the Mythras ruleset. It has most of what one needs to start building new RPGs.

Casus Mus is based on Mythras Imperative, and is thus also ORC-licensed³. This site intends to provide all of the necessary rules to play the Casus Mus roleplaying game.

What's Good About Mythras?

Like most RPGs in the BRP D100 family:

Mythras is skill-based, classless, and does not have levels. Most action resolution mechanisms in Mythras use skills. Characters can be crafted using setting, background or backstory, culture, profession or career, and the player's imagination.
Hit points do not, in general, increase as characters improve. This means that combat always has consequences, and a lucky novice can be just as dangerous as a seasoned warrior.
Character improvement happens through skill improvement and acquiring new skills and powers.

Perhaps the most compelling thing about the Mythras system¹ is its combat system and the action economy.

Mythras uses an active defense combat system, where someone being attacked has the opportunity to take actions to defend themselves. Contrast this with a passive defense combat system, where success or failure of an attack is based on the attacker's actions, and the defender has no opportunity to affect the outcome.

Some Mythras combat system concepts are:

Combat Styles: Skills representing a set of weapons and fighting techniques; Combat Styles may be learned through one’s culture or career, or may be learned as a hobby. Combat Styles are the skills used by attackers and defenders in combat.
Combat Style Traits: Think of these as static feats, unlocked by the particular training involved in a Combat Style. Combat Style Traits grant Combat Styles advantages under specific circumbstances. For example, the Mounted Combat Trait allows a character to ignore the skill cap ordinarily placed on combat rolls by the Ride skill.
Combat Maneuvers⁴: Think of these as dynamic feats, unlocked by a level of success of one opponent over another. Combat Maneuvers include things like disarming, tripping, stunning, or pressing an advantage to prevent an opponent from taking other actions.

Mythras' action economy allows characters a certain number of Action Points each combat round; these are spent in proactive or reactive actions, and allow a character to do more than one thing in a single combat round.

In my opinion.

Mythras is a descendant of the Basic Roleplaying system.

License is not copyright. (Note that that link refers to software and open source licenses, but the concepts are more or less the same.)

⁴

Combat Maneuvers are called Special Effects in Mythras.