Silk Hearts are how Hornet regains the power necessary to regenerate a segment of expended Silk in Hollow Knight: Silksong. There are three of these Silk Hearts spread around Pharloom, and getting the first one is how Hornet can initially begin recovering Silk automatically, instead of being dependent on attacking enemies, destroying Silk webs, and the occasional finite Silk spindles.
This Hollow Knight: Silksong guide lists the locations of every Silk Heart to be found in Pharloom.
The Marrow
Defeat the Bell Beast in The Marrow to acquire the very first Silk Heart. Requires Silk Spear to even access the boss.
Whiteward
Begin by getting the Surgeon’s Key from the far left of the topmost tunnel on the right side of the region. Next, head to the lock situated diagonally opposite to this location, in the far left bottom of Whiteward. This leads to a boss, The Unravelled, that must be defeated for the Silk Heart.
The Cradle
Defeat Lace again, in The Cradle.
Finding all three of the Silk Hearts will unlock the trophy/achievement “Regenerated”.
Those are the locations of all 3 Silk Hearts to be found in Hollow Knight: Silksong.
