I would like to solve this question. We can 'spawn' Carniphila while doing Foul Spirits task in 'An Uneasy Alliance Quest'.
NPC Curos sends us east to calm the spirit of the tree.
We have to stand on the field with blood and play on . We may not always be able to complete the task after first use it. In case of failure, 2 monsters Haunted Treelings or 2 monsters Carniphilas will respawn next to us.