Vampire Rose
Yet another blood-sucking plant, this time in the CR 3 package of a rose bush. Moving on...

Ahh, now here's a Plant-type monster I can get behind. These tribal plant people area born from the carcasses of creatures slain by the russet mold (a hazard we'll meet later), creating a somewhat macabre fungal-based ecology. Even better, the vegepygmies cover a range of levels, from the CR 1/2 worker to the CR 5 chief, so you can use them as extended recurring enemies in a campaign. Worthy of note is that, in addition to the low damage reduction and immunity to electricity all vegepygmies have, the chief has the ability to produce spores that, if they kill a creature, cause its body to sprout a CR 4 vegepygmy bodyguard, meaning that the highest of the vegepygmies have little use for the russet mold in their life cycle anymore. If you want a different horde than your bog standard goblins or orcs, I'd say give the vegepygmies a look.

Also known as the tunnel thugs, these CR 1/2 Aberrations prowl the deepest reaches of the earth, using their at-will meld into stone supernatural ability to pop in and out of walls and surprise prey and unsuspecting adventurers. They're a novel creature, but they are also rather bland at face value, so they're probably something you want to mold and fluff to your own liking.

Volts are big-headed, long-tailed lightning creatures, small Aberrations of the underground whose origins are unknown to our sage friends. They have a blood-sucking bite and an electricity-producing tail, so both ends of the creature are equally hazardous.