Finvarra can be a tricky opponent at first, but learning when to attack is key. After every attack he'll "reset" his stance, attack then. He carries around a one-handed sword, like your character would use. He also uses his hand as a shield, much like with Siegfried, he will counter your attack completely if you hit it.
Standard Combo: Finvarra will attack you in the same way you use the one-handed sword, but sometimes he'll stop after one strike, two, or even three.
Counter: If you hit his shield, he will counter with an upward slash, then spins around slashing you back. This is not dodgeable or guardable.
Turning Slash: Exactly like the Battle Art for the one-handed sword. He has a quick recovery from this.
Stinger: Finvarra will charge up then run at you with the sword piercing forward. After a set time, or getting to you, he will stop then lunge once striking downward. This attack will arc around you if you are not in front of him.
Ground Shockwave: Finvarra charges up, holding his sword up, then slams the blade of the sword into the ground sending a shockwave at you.