The phrase when a permanent enters the battlefield refers to whenever a permanent is put onto the battlefield, regardless of how it got there
The mana cost definitely holds it back, but if you end up with a good mana base that can actually make this happen, obviously enough, Tiamat will feel like a bomb
Torture Pit is a room that only adds two damage, but that damage is only dealt to opponents, not yourself
The seller is "cheefung2011" and is located in Selangor
Add on the potential to do all that for just two mana if you draw this off the top of your deck, and you've got a card that is likely to see itself in many black decks whether they focus on reanimation or not
Some cards can be purchased from the in-game store, but most are only available for a limited time during live events