Jumping/Plunging attacks performed by players cannot be parried under any circumstances.

Lorian, Elder Prince (You can't Riposte).

Dragonslayer Armour (You can't riposte).

Farron Greatsword (only while two-handed or using a shield with Weapon Skill).

Rotten Ghru Curved Sword (left hand only).

Painting Guardian's Curved Sword (left hand only).

Pontiff Knight Curved Sword (left hand only).

Darkdrift has shield splitter and Frayed Blade can not parry while holding)

Golden Wing Crest Shield (can also Spell Parry).

Sacred Bloom Shield (can also Spell Parry).

The exact timing varies depending on the parrying tool being used and the opponent's weapon, but in general, you want to initiate a Parry just before the opponent's attack would hit you. Parry is a Skill in Dark Souls 3 that allows you to deflect most melee attacks if timed properly, leaving your opponent in a vulnerable state and allowing you to follow up with a Riposte for incredible damage. Repel an attack at the right time to follow up with a critical hit.

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