Power Levels

Power Levels are a statistic that tells the game how strong a given Droid is. This lets the game be able to determine what a Droid becomes when rerolled, with rerolls giving a different Droid of the same Power Level. However, it also determines what type of Droids can spawn from a Mystery Button, or from killing a Droid with the Random modifier, with these cases spawning a Droid with a Power Level equal to the droid with the modifier.

Droids with a Null, or unmeasurable Power Level
if a droids power level is Null, that means that it is (or was) possible to change their power level/type in one way or another, if it's unmeasurable, that means that the droids power level/type cant be changed through any means (except for jei if they really wanted to do it with the power of being the developer), the thing common about all droids that are deemed a power level of Null is that when its power level is changed (or if they're rerolled in any way, even if power level wasn't changed) is that it results in a useless droid replacing them 100% of the time, and any droid in this category can only be spawned in specific ways, and cannot normally be spawned outside of those ways (useless droid is truely useless, having no speed, no aggro range, no damage, and drops nothing), before 1.5, rerolling these droid resulted in a weak droid, and it is assumed anything unmeasurable resulted in a useless droid as well, but it'd be impossible to figure out without hacking, and those with unknown just have not been tested on and are now assumed to be entirely removed from the game, thus making any chances with them impossible

The Shadow - Null, you can change it during the fight with The Dark One

The Phantom - Null, can be changed in The Darkness

The Corrupted - Null, can be changed in The Darkness

The Dark One - unmeasurable

RHJvaWQgb2YgVG9tb3Jyb3c= - Null, can be changed in Respite

jzbg4+J' AScc09Qn[zc=d - unknown

statue droid - Null, can be changed in Stone Sanctuary