Piercing Shriek is a Vampirism power that stuns enemies with a banshee-like scream. You unlock it with Brencis's blood, either from a phial in Xanthe's Recruiters: Taste of Power or at the end of Our Rotten Roots.
Our Rotten RootsOur Rotten Roots is the fourth quest in Lacra's questline and takes Coen into Anachora, a realm built from memories. It pays out well, with 1000 XP, a skill point and the Piercing Shriek vampire ability.In Xanthe's Recruiters: Taste of Power, deal with Xanthe's Blood Guard recruiters, inspect the reliquary and take the blood. Drinking the Phial of Brencis's Blood opens the ability. Then learn it at a road shrine with a skill point and Corruption.
The shriek stuns enemies around you, which buys space for a bite or a heavy hit. Murohni use it against you too, so expect it in lair fights.
Image: Rebel Wolves / Bandai NamcoBlood Surge
Blood Surge is a night-only Vampirism ability that makes a target burst from the inside through their own blood. You unlock it by drinking Xanthe's blood, so it is tied to her questline.
Compel Soul
Compel Soul is the first Witchcraft hex Coen learns, from Anca, after Laslea is sacked. It makes the recently dead replay the moments before they died, which is how you crack many investigations.
Crimson Rush
Crimson Rush is a Vampirism power that makes your active abilities hit harder the healthier you are. It is open from the start, so you only need Corruption and skill points to learn it.
Mesmerise
Mesmerise is a Vampirism power that lets you take control of an enemy's mind. You unlock it with Lacra's blood during The Night of Horrors, so it comes from story progress.