When two cards are exiled and melded, they each leave the battlefield, then return together as one new untapped object with no relation to either of the objects that left the battlefield
Otherwise, you draw a card and Gollum can't be blocked this turn
Threats are the most important part of Modern, and answers arent as ubiquitous as they are in other formats
In a game where you almost exclusively create your own decks, having that feeling of surprise as you draw each card makes for a far more exhilarating experience
The tapped entry is a serious downside here because mono-white decks usually play a low curve, and its a major hindrance if you fail to play a mana rock or a turn-1 creature beacuse this is your only white source
The real trick is to pair it with cards like Temporal Trespass and Brainsurge to manipulate the top of your library and maximize damage triggers