Aldarc
Legend
At its heart, Cortex is a roll and keep system where characters assemble a dice pool, often of different die types, from their applicable trait sets,* roll, and then add the two highest values. Players may also pick a die type from the roll - e.g., d12, d10, d8, etc. - to serve as the Effect/damage of the roll. The GM may use a static number for the opposition or roll the opposition pool from whatever resources they have available.Is there a good summary or detailed review of Cortex? This is the first I've heard of it, and as a relentless tinkerer with systems, it sounds interesting, but my Google-fu is weak.
* Traits are one thing that make Cortex more difficult to pin down. Players typically have 3-4 prime sets. When assembling a dice pool, it's usually only one die from each set. The list of Traits vary a lot between games of Cortex: e.g., Values, Relationships, Skills, Attributes, Roles, Assets, etc. The only Trait that is consistent is Distinctions, which are much like Aspects in Fate in that they are three fictional descriptors of your character. Distinctions are each rated at d8, but players can downgrade their roll, if one of their Distinctions could work against them, from a d8 to a d4 to earn Plot Points that can be used in various ways.
Cortex is a classless and levelless system as well. Class-like dials and knobs exist, and character progression exists, but it's like Fate where the games are typically less Zero-to-20 Levels of Hero sort of deal. I believe that @angille's Mythikal utilizes class-like Disciplines, but I'm not sure how they work.