I'm not a native speaker of this language, and I can make some grammar mistake and etc. I'll try to explain clearly. I didn't use any translater and relied only my language skills.
You may add me to friends in Steam and help with English If you want to. I would really appreciate that.

1. Summon "Flock of crows"
That attack permanently give you the Blindness status. It affects map world(you will see worse than usual, almost you'll see darkness) and You'll often miss in a battle.
2. Maul attack
usual crow mauler's attack that can give a permanent "broken bone" status and It attact your damage status. And reduce your max hp
3. Peck
a fatal attack, kill you and your friends once.

So, you should have:
1. Eastern perfume
2. Red vial
3. Lron Mask
4. At least 2 characters
5. Weapons with high damage
(Blue sin, Claymore, Eastern sword, or Bone shears)
Equid one of yours characters the mask and perfume.

First of all you should throw red vial on the Crow Mauler's head
The Second step, all characters should target on the crow mauler's weapon
Then after that the characters should target on the body(torso)
If He summon the crows they will attack that character who equied the Eastern perfume and wears the Iron mask.
There is a high chance that Crow Mauler attack on the character with perfume(but It's not 100% that will happen)