ASH KETCHUM DAVIS MOTOMIYA UZUMAKI NARUTO SON GOKU THAT KID FROM BEYBLADES HUNTER STEELE:
Our hero. He's just like every other hero in every other anime. Not much to talk about. He's impulsive, perpetually happy, prone to facefaults, and completely unable to stand still for five seconds straight. He fights with a spear-sword-thing. According to the prophecy, he may or may not be destined to destroy the Inner World, probably by tripping over a support pillar or something. By all rights, he should be dead on at least five separate occasions per episode, but Lady Luck favors him greatly. I bet he's sleeping with her.
SHADOW THE HEDGEHOG: Hunter's spider. He's one of those snarky, no-nonsense, go-it-alone types who is reluctantly forced into a partnership with some ineffectual moron because if left alone he'd get too much shit done. Resents Hunter, but has to admire the kid's bravery, a word which here means “idiocy”.
MISTY CORONA:
Secretly the youngest of three sisters and therefore one of the leaders of the Cerulean City Spider Gym, Corona is currently following Hunter around because he crashed her spider and now he owes her a new one. She serves as a bland love interest for Hunter and not much else, honestly. She fights with bows and arrows and I think she has healing abilities because she's a girl and that's what girls do in fighting shows. Prone to glowing, because she's special, by which I mean she's just like every other girl who fills her role.
VENUS: Corona's spider. Has a thing for Shadow. She's here to fill a role, just like Corona, but as a steed rather than a stock character.
BROCK GUY CECIL MAGMA:
The Big Guy. He's our ineffectual loner, operating separately from Hunter and Corona except for every single moment he appears onscreen. He's level-headed and calm and would rather be breeding spiders than using them in battle. He's also supposed to be helping his partner spider find its little sister or something.
BRUTUS: Magma's spider. He's super strong and he's looking for his sister, Portia, because apparently being an armored robot spider just isn't gimmicky enough.
IGNEOUS:
Arachnia's Captain of the Guard. Young-ish (probably older than most of the rest of the cast), arrogant, super-serious, and has hair resembling an electric toothbrush. He's Roy Mustang to Hunter's Ed Elric, except Fullmetal Alchemist has interesting characters.
FLAME: Igneous's spider. He doesn't talk much. I suspect it's because his ability to shoot flaming web has scorched his vocal cords beyond all usefulness.
GARDENIA PRINCE LUMEN:
Ruler of Arachnia and somewhat of a troll. He's laid-back and very casual, with an exceptionally high intellect and a bit of a Casanova streak, which is weird because he appears to be twelve. He prefers diplomacy to combat. It's unknown if he's actually a pacifist or he's just too lazy to clean up after his insanely overpowered spider, Ebony.
EBONY: Lumen's Spider-Hulk partner. Another mostly silent type, as what little screentime he has consists of him breaking everything in sight and scaring the crap out of everyone.
PRINCESS SPARKLE:
Lumen's little sister and the show's token loli. She doesn't do much except sit around and be cute and have the best fucking name ever. Suspected to be a My Little Pony in disguise.
HOTARLA: Sparkle's spider partner. Too young for battle, so she just sits around staring at Sparkle with her enormous eyes and acting all timid and adorable.
KEN ICHIJOUJI REX RACER TOMMY OLIVER AQUNE:
The Racer X of Spider Riders. She's being mind-controlled to work for the bad guys. She changes sides halfway through the show, which sounds like a spoiler, except you totally saw it coming.
PORTIA: Aqune's partner and Brutus's missing little sister. None of that is spoiling anything, because you liked this show better when it was called Digimon.