So next session my party is fighting this creature called a Nullborn. The idea behind it is that it is a monster made from a person whose body was unstable when it comes to magic at the highest degree. The result is an entity that bends the laws of physics slightly and absorbs magic/life force from all those around. The goal imo is that this should be a somewhat scary monster by itself but in groups would be devastating. Right now they are facing one has an introduction. My party is 5 level 4s and are mostly at full health though low on spells.

I’ll be honest I’m new to DMing and that means new to making homebrew monsters so I did use ChatGPT a bit to give me a baseline. I based it off of a Nightwalker but severely toned down. I’d like some input on things I should consider, if I should buff it to make it a scarier but manageable fight (since they’ll have action economy on their side), or keep it the same.

Here’s the statblock:

I'd like to introduce a creature in an upcoming campaign with the ability to create a sort of mirage around itself using illusion magic. The creature is a miniature version of a 2e living spelljamming ship called a smalljammer. They don't typically carry weapons but instead disguise themselves as other creatures and objects of similar size for protection.

If possible, I'd like to copy an ability from another monster just to avoid having to word the ability carefully (the creature would likely end up in control of a PC as a sort of pet). The first things that came to mind were creatures like mimics and changelings. However, the way I understand the 2e ability is that it is more of an illusory facade rather than a transformation, and with the ability to disguise as both creatures and objects instead of one or the other.

Thanks in advance for any help, hopefully I'm asking this in the right place.