In Master Duel, players get a lot of free in-game currency when starting their account, enough to build essentially any single deck they want
If your opponent discards a card while you control Leyline of the Void, abilities that check whether a card is discarded (such as Hollow One, or a madness ability of the discarded card) still work, even though that card never reaches that player's graveyard
Second, his other ability lets you discard a card to counter a spell with the same mana cost, giving your new hand many interaction options
Each constellation bonus is different
Seriously though, Manglehorn is the latest in a long line of "enters the battlefield and destroys something" creatures, and it's definitely caught the attention of the Vintage community
Upon release, it is evident that the templating of the cards effect is not intuitive