Cover Art by Sai Kayden
Third party publishers followed suit with their own ideas, but given the brevity of mechanics it's not often that an entire product is dedicated to them. But Secrets of the Masquerade Reveler is a worthy exception, detailing a Barbarian archetype who accesses a pool of Eidolon Evolutions while "raging" to represent alternate states of being. The concept is a person whose close encounter with the fey realms gifted them with the ability to assume the traits of entities and ideals by undergoing a trance-like state known as a Masquerade which replaces the base Rage ability.
While in this Masquerade, the reveler can don "Masks" modeled off of fey creatures and certain professions in the form of 4 to 8 Evolution Points per Mask based on class level. A Pixie Mask can grant flight and personal invisibility, the Sage's Mask can grant +8 bonus to most Knowledge checks, and so on and so forth. Masquerade Revelers gain one Mask per level, and potentially more with the Extra Mask feat. The base Evolutions are versatile enough, but the archetype has a host of new Evolutions specific to them such as Fey Magic which grants access to some illusion and nature-based spell-like abilities.
Although it is possible for a player to create one's own Mask, a healthy portion of the book provides many sample Masks, all grouped into types such as Fey, Gremlin, Forbidden, Beast, Mythic, and Tane Masks. These are not just flavoring: several new feats within this book grant access to Masks of certain types, and some Evolutions can only be taken with said types (such as quadruped abilities and Beast Masks). Even with the samples provided, one can see the Masquerade Reveler adequately serving a variety of roles: the Jinkin's Tiny size with Skilled in Disable Device and a later Dimension Door ability is a tailor-made scout, while the Dweomercat's Pounce ability is a welcome addition to any melee-focused character. And that's not covering the Tane Masks, who represent the most powerful of fey lords such as the Jabberwock which can grant flight, twin fire-based eye rays, and Huge size among potential other abilities.
Although the Masquerade Reveler gains quite a bit by trading away standard Rage and its expansions, the class is at once versatile while not being game-breaking. The Masquerade ability is still keyed off of a rounds-per-day resource, so it doesn't have the long-term staying power of primary spellcasters whose effects can last for hours or even days. But access to flight, +8 for skills, tremorsense, radius auras, debuffs, Pounce, and many other abilities make it able to do a lot more things than most Barbarians and martials. The in-character fluff text and explanations of certain Masks and revelers is cool and provides inspiration for interesting character concepts. You can get a lot of mileage out of it as both a player and Game Master with the options provided.
For those interested in the mechanical side of things, I provide an in-depth look at the archetype and its many features in this thread.