Swampire

From the Super Mario Wiki

Paper Mario: The Thousand-Year Door Enemy
Swampire

Max HP	20
Attack	6
Defense	0
Location(s)	Pit of 100 Trials (Floors 91-99)
Log	A feared health-sucking bat that lives in the darkness. It steals your HP to add to its own.
Items	None
Moves	HP Drain (6)
Tattle	That's a Swampire. It's a feared health-sucker that hides in the darkness. It sucks health from its prey to add to its own HP. And that... totally grosses me out like you wouldn't believe. If you let it feast on you, its HP will get really high. Focus your attacks on it!
Bestiary 65 66 67

The Swampire is a green version of the Swooper in Paper Mario: The Thousand-Year Door. A feared Swooper that hides in the darkness. It can suck Mario's health and add it to its own. Because of their high attack power it's recommended to use a Dizzy attack item first, or use a Boo's Sheet or a Volt Shroom or wear the Zap Tap Badge. Bobbery's Hold Fast works too. The name of this enemy is a pun on the words "vampire" and "Swooper". Swampires resemble the Swoopers from Super Mario World, as they, too, were green.