If I send it back to the library, should it still be allowed to come back out? Or was I just having the worst luck and my opponent had a hand full of them? I tucked it at least 5 times.
By the time i finished that game, i had cast 28 supports and 27 eldrazi. 
If you’re using something like Gone Missing, it just puts it on top of the library. It’ll always come back out soon.
well then maybe they were just getting good matches. cause i think about 4 of the times, they were able to cast it immediately after.
The cards that bounce a creature back to the library usually puts it back on TOP of the library. Try using Days Undoing to force the library to be shuffled (providing you have it)!
Probably had one in hand gaining mana, and the other getting bounced to the top of the library.
as the name implies, it’s eternal.
It’s a 3/3 for 12 that literally dies to everything. That’s not a threat. It’s a speed bump. You should hope and pray that your opponent’s hand is clogged up with this creature, because you will win that game. A 3/4 creature without flying will kill this thing twice. Meaning that your 4 mana Devil’s Playground, 5 mana Oath of Gideon, even a freaking Sigiled Starfish will send this creature back to your opponent’s hand, forcing them to cast it and recast it. They need to spend 36 mana on this creature just to be able to kill a non-reinforced Sigiled Starfish. But if you’re producing mana at the same rate, your Starfish is now a 12/20 which draws you 2 cards per turn. (12/11 if it runs into the speed bump three times).