Krenko, Tin Street Kingpin: Well, well, if it isn't the goblin mobster of Ravnica's underbelly
Do you use any planeswalker tutors, especially the intro deck rares
Greasefang, Okiba Boss Greasefang, Okiba Boss is certainly no slouch as a vehicle commander, but I wouldnt really use it as a rat commander unless I were going purely on theming
Creme, es normal abrumarse
The Darkness Crystal is fine and might actually be a funny sideboard card against the sacrifice decks because it turns off death triggers, but its usually not worth the mana investment
You can do worse, but since this is an artifact (and again, an artifact in a format where theres no payoff for playing artifacts or having them be in the graveyard), you can also do better