In Elden Ring, there are two halves of the Haligtree Secret Medallion (Left and Right) because the game's designers wanted to create a sense of exploration and discovery
To find one half of the Haligtree Secret Medallion in Elden Ring, follow these steps
Haligtree Secret Medallion (Left half):
Go to Castle Sol.
Defeat Commander Niall.
Find the medallion on the roof of the northeast tower.
Haligtree Secret Medallion (Right half):
Go to the Village of the Albinaurics Site of Grace.
Head west of Liurnia of the Lakes and enter the swamp caves.
Find Albus, who is disguised as a pot.
Hit Albus with your weapon or roll into him to break the illusion.
Get Haligtree Secret Medallion (Right) from Albus.