Each time the scarlet flower blooms, Malenia's rot advances ... near the Haligtree Roots Site of Lost Grace. Scarlet Aeonia has no associated Rune cost, and can be acquired for free from Enia.

The Ash of War: Poisonous Mist is a drop from a Teardrop Scarab that appears deep inside the Swamp of Aeonia in Caelid. You must first locate the Aeonia Swamp Shore Site of Grace to find it.