Things I've seen but can't work out

[Ev3rNites]

Parry
Fire shield?
and thing that makes the stage change to the arcana of the person who used it

What are these things and how do I perform them?

[Doggywara]

If you want a parry this game, you pick Kamui.

What's fire shield?

You probably mean EF state

EF is done by pressing all three top buttons. ABC.

I need more details to actually answer this right.

[sbr616]

Parry: Akane and Kamui have some counter moves; Punishment Arcana has a counter super; there's clash when two clashable attacks intersect (some attacks can be clashed on their startup)

"Fire shield": probably is the forward guard cancel (called 6GC, because 6 is the direction notation for "forward" in fighting games, with your character facing the right side of the screen -- there are directions from 1 to 9, they're analogous to your keyboard's numeric pad), which costs one super meter (the arcana gauge at the bottom of the screen), has some invincibility period followed by a clash period (a period where whatever clashable attacks hit the character moving forward with that "shield" will result in a clash, visible by some lightnings coming from the attack while the screen gets dark for a short time and "intersect" appears on the screen)

the screen will change when one of the players use the Extend Force (weak+medium+strong attack -- a.k.a. ABC buttons -- while standing on the ground, needs the force gauge -- at the top corner of the screen -- to be at 100%); Extend Force can be activated when your character isn't doing anything, or is in the middle of a cancellable attack (not all attacks can be cancelled) -- a lot of arcana attacks can be cancelled into Extend Force even when they miss their opponent -- or is blocking; Extend Force has a variety of uses such as temporarily improving your characters' damage, movement speed and attack speed, activating arcana-specific effects (listed in the arcana's command list when you pause the game), giving you access to their Arcana Eclipse skills (214BC, or down->down/back->back + medium + strong), or Arcana Blaze (236ABC, or down->down/forward->forward + weak + medium + strong), both Eclipse and Blaze require you to be standing on the ground (Arcana Blazes are powerful but put your force gauge into a long cooldown, close to how long an Arcana Burst -- CE, or strong + arcana buttons -- would).

neutral (a.k.a. "when doing nothing") Extend Force activation has the longest duration (the normal duration), while its other two variations (EFC -- short for Extend Force Cancel -- and its Guard Cancel version) have reduced duration; neutral EF and its guard cancel version (not its EFC version) also have a blast effect which pushes the opponent away from you (for no damage), known as Extend Blast, and it can be used to counter incoming opponent attacks or to deal with the opponent hitting your defense, if you feel like the opponent will soon get through your defense; however, if the opponent blocks the EB, you take a longer time to return to neutral (after which you can block the opponent's attacks) and is susceptible to being attacked (to put it shortly, you can be punished if your opponent guessed right about you using EB, and you guessed wrong about the opponent being hit by the EB)