Siolvas, the Aberrant Goddess of Undeath.
Daughter of Rionn'ath. BBEG.

She was once the partner of Iúnas, but saw the first mortals as a plague rather than people to live alongside. Iúnas saw her downfall, but instead of true death, she was fractured and scattered throughout existence and beyond. It's taken her many, many years to regain her power.

Meilus follows her, and was there when she first rose to power.
Adaliah is her 'puppet'. She's been breaking her for over sixty years, and will continue to do so until she has no more use for her.

Tbh, her main reference is a little outdated now.
The Void Herald is one of her minions from beyond the veil of reality. They're completely alien to existence, and the closest most people can come to comprehending them as is an absence.

Other Athrei Gods:
• Aimhirghin, the Silver Harper
• Airegeith, the Mortal Deceiver
• Cearrbha, the Shattered Moon
• Ghao'threk, the Founder of the Arcane
• Iúnas, the Hand of Justice
• Rionn'ath, the All Creator
• Scáth, the Nightbringer
• Siolvas, the Aberrant Daughter
All Deities and their symbols.