I haven't seen anyone talk about this but I think that Spirit Ashes will respond to the type of damage you are doing and try to stack their own. In this example
Spirit Ashes in Elden Ring: Where to find and how to use them | Digital Trends
Omenkiller Rollo | Elden Ring Wiki
Rollo Termal Clasico
This Spirit Summon is Overpowered | Elden Ring OMENKILLER ROLLO Location | Rare Spirit Ash - YouTube
Rollo Termal Clasico
Elden Ring [Omenkiller Rollo Spirit location in the Capital Outskirts] - YouTube
ROLLO TERMICO SPIRIT CLASSIC - KOMUNE SUPPLIES
Rollo and the Woods Spirit ( Rölli ja metsänhenki ) [ NON-USA FORMAT, PAL, Reg.2 Import - Finland ] - Walmart.com