When you perform your ValdaSpire24 ritual, you can choose to plant corpse flowers in any of your thralls, causing each such thrall to have the following benefits.
Plant
The thrall is a Plant instead of an Undead, but counts as Undead for the purpose of your Necromancer features.
Necrosynthesis
Whenever you take a Short or Long Rest, the thrall takes root in the ground and regains Hit Points equal to 1d8 plus your Intelligence modifier.