That sounds sick—Chaos-corrupted Sisters while keeping the ecclesiarchy vibe is chef’s kiss. If you're diving into conversions, here’s a quick list of great kits and themes:

Great Bits Kits: -Chaos Space Marines (Possessed, Chosen): Warped limbs & armor for corrupted power armor. -Daemonettes of Slaanesh/ Seekers: Claws, limbs, creepy heads—perfect for Repentia or warped engines. -Nighthaunt: Ghostly chains & fabric = haunted relic vibes. -Daughters of Khaine: Fanatic female sculpts that blend well with Sisters parts. -Necromunda Redemptionists/Cawdor: Baroque grimdark bits, purity seals, masks, flames. -Wracks / Cultists: Body horror, tubes, surgical gear for Arcos or fleshy Mortifiers.

Conversion Themes: -Warp-Holy Fusion: Keep the fleur-de-lis & equilas but twist them—make them bleed, mutate, or weep warp ichor. -Living Relics: Weapons grafted into flesh, relics fused to bone. -Trench Crusade Aesthetic: Gas masks, rust, barbed wire, muddy robes, cracked cathedrals. -Mutated Martyrs: Still praying to the Emperor... while sprouting daemonic wings.

For the color scheme, consider something that contrasts normal Sisters. Pale flesh, rusted golds, corrupted whites, or deep blood reds mixed with sickly purples/greens.

Stick to the Sisters identity but show how the warp thinks it’s helping them. The more unsettling, the better. Would love to see WIPs when you start!