Both of Karn's abilities net card advantage and his minus gives you a sizeable artifact creature as the game goes on
Krenko, Mob Boss Goblin Tribal Commander Deck
Cards like Blood Petal Celebramt Olivia's Attendants, Dominating Vampire, Welcoming Vampire, and Markov Purifier tend to blur together into one mass of brown and grey, especially when compared to standouts from the style like Cemetery Gatekeeper, Odric Blood Cursed, and Runo Stromkirk
This way, you can skip the underpowered ones and go straight to drawing three extra cards, particularly when Sapphire Medallion let you do it all on the cheap
For more continuous effects in white, youd be looking at creatures and effects that want battlefield presence
The other two abilities are also helpful, but the goad is the big money play here