I faced this guy in Legacy Training Grounds today:
Dev Planeswalker
level 10
150 life
+4 bonus all colored mana
Abilities:
Pick Creature (0): Pick one Creature in library. It gains full mana
Pick Spell 3 (0): Pick one Spell in library. It gains full mana
Pick Support (0): Pick one Support in library. It gains full mana
I can guess this guy is for dev to investigate bugs, but should he be showing up in TG? Has anyone else had the pleasure?
Hi @Bubbles_CS
Thank you so much for the heads up and we apologize if it harmed your experience in any way!
We needed to test something on the Live and since this tester Planeswalker is invisible for players, we thought you would not be able to see it.
Our mistake :s
Thank you for your patience,
Marcela.
@Oktagon_Support No issues finding this guy in Training Grounds. It sounds like I just had a lucky match 
I was just farming my daily 10 and he fell just as quickly as anyone else to Hazoret’s Undying Fury / Deploy The Gatewatch combo.
I’m not sure I’d want to Face this in an event where I was playing something more fair, though!
Just thankful there was an actual excuse instead of us finding out that some hackers had found a way to dig that up out of the code and utilize it.
It has a horrible face. LOL
It’s Part of the card art from Unraveling Mummy if you didn’t recognize it. I don’t know why anyone would choose it, though 
Cowboying it in production (or spoofing a user) is sometimes the only way to confirm/refute a defect.
It’s pretty dang cool that they’re doing this to chase the bugs we report.
