This is flying, so it's safe, and if you put 5 into X, you'll now have a 7/7 that'll kill in three Commander Damage hits
(5/3/2019) If a permanent leaves the battlefield this way but ends up in a zone other than a library (most likely because it's a player's commander in the Commander variant), it's still counted to determine how many cards to reveal.
I ended up needing to manually add my custom cards after the script was done, but once I managed to save my order on MPC, this was pretty easy
If you ever see someone discard two lands to Bandits Talent in the early game, its a great time to follow up with targeted discard whatever non-lands they hold are clearly worth protecting
For example, you could activate Stampeding Scurryfoot's Exhaust ability to create a 3/3 Elephant, then find a way to blink or bounce the mouse