Heartstone

What we know

Night-hag component; mottled green, slimy, faint glow; pulsing (Session 21 @ 00:15:23)
Morgantha kept it in her neck pouch at Old Bonegrinder Windmill (Session 21 @ 00:15:23)
Hags use heartstone to escape into the ethereal plane when in danger; must catch hag away from stone or bargain (Session 19 @ 01:17:27)
Sildir Investigation 13 found it on Morgantha after coven defeat (Session 21 @ 00:15:23)
Sylalys carried it after looting; delivered to Victor Vallakovich in a bag (Session 21 @ 01:35:09)
Lady Fiona Wachter briefly examined it; Sildir intimidation 24 returned stone to party (Session 21 @ 01:06:34)
Victor: ritual midnight at full moon—planes closest; needs heartstone in salt circle (Session 21 @ 01:39:02)
Saturno anchored heartstone during Stella ritual; Strength 18 with Mercurio's Enhance Ability (Session 22 @ 01:12:00)
Stella's soul returned to body—ritual succeeded (Session 22 @ 01:12:00)