Zetterburn has the unique ability to burn opponents, causing them to continuously receive residual damage (think Lip's Stick from Smash Bros). He's pretty well-rounded, and his moveset reminds me of a combination of Bowser and Fox, if you can picture that.
Orcane has some pretty interesting mechanics based on his Neutral B move, which generates a puddle. Up+B lets you teleport directly to the puddle (so for example you can juggle someone offstage then teleport back to safety when you're done), while Down+B turns it into bubbles for a defensive measure, and standing on top of it while doing a Strong Attack (this game's Smash Attacks) will improve his range.
Wrastor is a bit unique as a character because his Strong Attacks are performed mid-jump rather than on the ground. He's also the resident quadruple jump character, and his Side B generates a wind current that he can use to improve his speed. His moveset is kinda reminiscent of Metaknight and Captain Falcon combined.
Kragg is probably my favorite character for one simple reason: his Up+B. It generates a pillar beneath him that acts as a platform that both players can stand on. It can be destroyed in one hit from either player, but it does have quite a few uses (ie: creating a platform near the top of the stage to KO someone faster, creating an obstacle for an opponent trying to get back so they HAVE to attack it during their recovery). He also has a rock-throw and a Sonic-esque spin for some reason, but it's all about the pillar.
Forsburn is probably one of the more confusing characters to use. He can make smoke screens with his neutral B that he can hide behind but his opponent can't. He can also use his Down+B to inhale his own smoke, and after inhaling three, he can "combust" which has very high launching power. Also his Side+B makes a clone of himself which can attack by doing B attacks, but it appears that he chooses his attacks based on his positioning so it's not really something you have complete control over AFAIK
Maypul seemingly has the worst Up+B in the game in that it pretty much does nothing. That is, unless you've used one of your other specials and "marked" your opponent with them. If your opponent is marked, your Up+B can be used to bring yourself right in front of him. So if you get launched and your opponent has a mark, reel yourself in!
Absa is all about setting up clouds for stage control. She can generate electricity from them as well, so part of the challenge is getting them to be either between Absa and he cloud, or just close to the cloud. She's also got some pretty interesting normals. Think Pikachu + Ness/Lucas with a little Mewtwo thrown in.
Etalus is a big, heavy, ice-controlling bear. He is capable of freezing the ground, giving him the ability to slide across it. He can also use said ice to create super armor or to freeze other characters. He's very similar to Donkey Kong, King Dedede, and SFIV's Hakan.
Fire Capitol is a pretty safe stage. No hazards at all, staggered platforms and a wall. Basic version just gets rid of the wall so that the ground is flat.
Music: HereAir Armada looks pretty normal except the middle has a giant spring! It activates by jumping whenever you're on top of it, giving you extra velocity in your jumps. Basic unfortunately gets rid of this but I guess it's understandable.
Music: Here (it's the song in the Early Access trailer)
The Rock Wall is pretty much as the description says. Has walk-off, but this stage's gimmick is that the platforms in the middle can be broken with attacks, making makeshift holes to knock your opponents into. Basic removes the walk-off and the platforms can't crumble.
Music: HereMerchant Port has a little ferris wheel of moving platforms in the middle. Additionally, the little machines on the side of the stages will blast water if attacked when the gauges are full. They don't do damage but the launch rate is pretty powerful! Basic keeps the platforms in the middle in one place and removes the machines.
Music: HereTreetop Lodge looks pretty normal but what are those glowing lights??? Green lights do nothing, but if you launch an opponent off the side of the stage with red lights and they're low enough, a carnivorous plant will devour them and K.O. them in one hit. Basic removes the plant.
Music: HereBlazing Hideout is pretty darn awesome to fight on. There's fire below the stage that will occasionally rise up and do damage ala Planet Zebes in the first Smash Bros. Basic gets rid of the fire.
Music: HereTower of Heaven is a guest stage from
an indie platforming game of the same name which flashygoodness previously worked on (it also had an appearance in Dan Fornace's previous Smash fan game, Super Smash Land). Every now and then a notepad will show up, and if a player collects it, they temporarily enact a law that the other players must follow for a temporary amount of time (ie: "Thou shalt not parry or dodge"). It's a little like Midgar in Sm4sh.
Music: Here(Sidenote: No, you don't automatically get Gameboy colors in this stage, every character has a gameboy palette as of the update this stage got added)
The game is
currently available on Steam Early-Access for $15, so anything outside of fighting on or offline is pretty barebones (as are some of the menus/music), and they are trying to bug-hunt at this stage.
That being said, it's looking to be an awesome game so far, and you should totally try it out if you get a chance!