While it looks tough to access at first, the card essentially gives you two land drops itself, one on entry and one when your Earthbent land is inevitably removed somehow, so it shouldnt be hard to get going
It is a one-mana legendary monkey pirate creature at 2/2 that, when it deals combat damage to an opposing player, creates a treasure token and exiles the top card of the defending player's library, and you can cast that card until the end of the turn
The best choice often lies in opposing commanders: Everybody wants to cast them frequently, so finding a common number does a lot
So if Karlach will likely die in combat, keep it from attacking and only swing in with your bigger threats
Thats also why the card disadvantage of playing Mox Diamond, Chrome Mox or Lions Eye Diamond matters far less, as games are faster and end much more abruptly