Elden Ring PC | Spiritcaller Snail boss fight solo on NG

You have to strike the snail, which teleports and is catalogued and all you can see is a glow of light.

Drops:
3,000 runes
Glinstone Sorcerer Ashes

Spirt-Caller Snail
"Spiritcaller Snail is a Boss in Elden Ring. Spiritcaller Snail is found in Road's End Catacombs and then again at the Spiritcaller's Cave. This is an optional boss, as players don't need to defeat it in order to advance in Elden Ring. However, doing so yields useful Items and Runes."
https://eldenring.wiki.fextralife.com/Spirit-Caller+Snail