This Fourm is made for those who are unfamiliar with Crisis: Equestria's cast. Keep train mind that may certain parts will be changed over time and they contain spoilers. Go here for the list of Antagonists.
The Protagonists of this story are the following:
Harmonia, the Goddess of Balance
Queen Blackburn
Flathoof
Lockwood
Briarthorn
Gilderoy
The Chronomancers:
Tick Tock
Time Turner (Doctor Hooves)
The Mane Six:
Twilight Sparkle
Rainbow Dash
Pinkie Pie
Fluttershy
Rarity
Applejack

Twilight Sparkle

A unicorn from Canterlot who serves as Princess Celestia's apprentice. She has a natural talent for Magic that goes far beyond what most unicorns are capable of. She's also very intelligent, levelheaded, and organized, making her the de-facto leader of the Mane Six.

As an Arcanist, Twilight is capable of channeling the power of the Stars, causing her power to grow in relation to the bond she has with her friends. Upon getting sucked into Equestria-V, though, she must learn to put her leadership skills into practice if she and her friends are to make it home in one piece.

Rainbow Dash

A speedy pegasus hailing from Cloudsdale who loves to race and compete whenever she can convince someone to go against her. Though Prideful and a bit arrogant, with a somewhat self-centered attitude, she's a loyal friend and a strong leader. Works as a weather manager of Ponyville.

Her main power allows her manipulate the weather on a far more powerful level then most Pegasi, as she is show the ability to manipulate lightning through her body to strengthen her Sonic Rainboom, or easily creating and controling a giant tornado.

She is also officially in a relationship with Pinkie Pie. Rainbow appears to have some issues with stallions that has not yet been addressed.

Pinkie Pie

Pinkamena Diane "Pinkie" Pie is a hyperactive earth pony who prances to the beat of her own percussion section. The sheer force of her cheerful personality can be overwhelming at first but anyone who shows a little patience with her eccentricities is rewarded with a truly unique and wonderful friend who fills every day with laughter. And musical numbers. And PARTIES!

Pinkie's power relies on a very crucial concept - believing is seeing. She can do just about anything she wants, so long as those who observe it and are able to comment on it believe in what they're seeing. Mentioning that what she's doing is impossible suddenly makes it very much so, and as such her allies have neglected to mention that to anypony outside of their sphere of influence.

Throughout the story Pinkie Pie uses pop-culture game and movie references very often, but most blatantly when in combat. She also tends to play a sample of music to go along with her battle scenes in order to pump herself up. She is later revealed to be officially in a relationship with Rainbow Dash.