Plant the in Denalan's Planter.
I have removed that foul moss from the heart, but it remains tainted...
Try placing the heart in my planter. It is filled with a nutritive soil that may cleanse and heal the heart.
This planter is filled with soil, specially prepared by Denalan.
You place the heart within the planter, and it quickly digs itself in!
A few seconds later it wriggles back out, cleansed. It pulses slightly... beckoning for you to take it.
The reward is a one-use temporary Guardian pet, likely the first one your character will have encountered.