The beastmen are a 2nd edition humanoid & the cloaker attaches to a WOUNDED creature and drains the damage off of it during the act of feeding, healing the creature in the process. It glows naturally during the feeding process.
According to its wiki entry, the Closker already has a “scientific “ name- Tenebra Complexor. Since the subspecies you describe is kind of an opposite of the main, we could call them Tenebra Inversus.
Bone ooze-unicelius bonius animatus?
It’s a form of ooze that makes bones move like a living creature that seems to be undead.
Viper tree-viperus psudoherbum
It a mixture of vipers and trees! Think a willow tree with viper heads in place of the branches!