Conjure Banderhobb

While speaking an intricate incantation, you use the component weapon to make a melee weapon attack on a living and incapacitated target amphibian (a frog, toad, or other froglike or amphibious creature).  Supernatural darkness then suffuses the target amphibian's body. This darkness transforms the amphibian into a large monstrosity called a Banderhobb.  The statistics of the Banderhobb are in Volo’s Guide to Monsters.  This creature is friendly to you and obeys your commands as your faithful thug, thief, and kidnapper.  The Banderhobb lives for a number of days equal to your spellcasting ability modifier (minimum one day), at the end of which it melts into a sticky puddle of foul-smelling black tar.  

While the Banderhobb is on the same plane of existence as you, you can cast this spell again to increase its hit points, using another amphibian.  If the tribute amphibian is slain, the Banderhobb’s hit point maximum and current hit points are both increased by the amount of damage that was dealt.  This process also extends the life span of the Banderhobb by one day.  You can have only one Banderhobb at any time.