It acts basically as a version of Terraforming that can place a field spell on either side of the field, but Terraforming is only limited
It's both an Eldrazi and an Octopus, so it plays into both your big creature groups, you can sacrifice another creature to make it cheaper (and thus have a target in your graveyard to reanimate later), and has Flash, so you can tap down four permanents whenever you cast it
Look for the round "Edition 1" stamp on the left side of the card, just below the artwork
It makes the playmat somewhat more exclusive too
The bad news is that Mana Vault is only legal in Commander, where it's on the list of Game Changer cards, and it's restricted in Vintage
There are plenty of times I find that I target myself, but other times, I have draw punishment online and it's delicious