As with other Secret Lairs, like July's MtG X Fortnite set, the Secret Lair X Post Malone: Backstage Pass and Secret Lair X Post Malone: The Lands sets will be gone for good once the preordering window closes.
The cards inside are most likely going to be unlimited, but in the event of a 104-04 postcode box with the 1st edition rulebook, you have a very slight chance of pulling no rarity cards
The other option is to take advantage of the direct damage, which is good in its own right to either finish off a damaged character or get them within range to be banished but also works with the likes of cards that benefit from being damaged - such as Scroop, Backstabber - that benefit from healing damage, like Rapunzel, Gifted Artist, or from damage being dealt: like Beast, Relentless.
Only time will tell, but I struggle to believe this is anything less than one of the strongest Izzet commanders ever printed
This Gitrog is now my third Golgari deck (Baba Lysaga, Night Witch and Tormod, the Desecrator // Kamahl, Heart of Krosa are my other two
Counters on the land remain on it even if they don't do anything.