Emerald City Knights is a campaign setting published by Green Ronin for the Mutants & Masterminds 3rd edition (M&M3e) rules.

Fenton was introduced to M&M3e when Green Ronin produced a version of the ruleset known as DC Adventures. This was a re-skinned version of M&M3e using DC characters and settings, but the actual rules were intact. A fan of DC (and comics as a whole) Fenton had been running a superhero RPG known as Heros for years - originally using the Storyteller system by White Wolf, then later using the Aberrant (a Superhero RPG) rules also by White Wolf. His setting was DC-centric, but used elements from Marvel and other comics.

DC Adventures began as the latest incarnation of the Heros game - why adapt rules when there was an actual ruleset, with proper character stats, etc...? Somewhere, the Heros title fell to the wayside in lieu of the title DC Adventures. But DC Adventures was a limited run, so he continued obtaining M&M3e products to have more to use - and he liked many of the elements in the pre-published "Emerald City Knights" adventure path. Although he didn't use the adventure path (but plans to use elements of it modified to suit his game), he liked the Emerald City setting, and the name "Emerald City Knights" as it was pun-ny, and sounded heroic. Always preferring to use established movie/tv characters as "guests" and patrons rather than key characters (so the players won't simply be in their shadow), he scrapped the official M&M3e world and instead placed Emerald City in his "Heros" version of the DC universe. Many of the characters made are canonical in the books (Mayor Talbot, Captain Wrath, Commissioner Hackman; some of the Sentinels - Dragoneye, Mongrel, Princess, Rocky, Xeno and Ultramarine) although a few have had their bios modified (such as the introduction of Patricia Hackman as his daughter and one of the city's elite Storm Breakers.

Of special note is the NPC Wyrmhole who has been around since Heros v2 and survived the game's setting retcon (although her personality was changed from essentially "wild emo girl" to "anime geek" which Fenton thinks has made the character a far more fun and lovable).

The character Equinox is also a special case - being originally introduced in an actual Aberrant system/setting game, and has been ported into Heros (v2+) but, unlike Wyrmhole, has not been retconned. Her background remains virtually untouched and it is the same Equinox that appears in various games of various sytems - both Aberrant, Heros, and even non-superhero games such as d20 Modern. She is capable of jumping across timelines and realities, and has essentially decided to "visit herself" in each of the infinite realities; seeing what she (and the world) is like in each one and, as she is funtionally immortal, when she find a world she likes decides to "stay a while" as she's not exactly worried about growing old and time is, literally, the one thing she can afford to waste.