If the target creature is an illegal target, you'll still gain control of the target Equipment until end of turn, but you won't attach it to the chosen creature
Id also consider running The One Ring, since the lifegain will nicely offset the burden counter life loss
This gives you not only card advantage, but a massive field-wide boost to your attacks
I have so many questions
The difference between these two card types has many implications: Moonmist Is Magics Only Mass Transform Spell This is much more niche, but the card Moonmist from Innistrad is pretty much the only generalist forced-transform spell in Magic, and even thats restricted to only transforming humans
If you could reliably cast this off of a Mountain, a Forest, and a Swamp, that would be great, but that's not an option