In many ways, Kenrith's deck is a good-stuff deck, using any powerful spells it can find in its five colors
I like the flavour, which allows you to draw 2 cards and discard 3 cards, symbolizing the idea of haggling over prices and value in a market
Skullclamp Theres a well-documented story that Skullclamp originally gave +1/+1, but the designers deemed that too powerful and switched it to +1/-1
Four colors is extremely hard to cast in the first place and even if you do manage to do it, he doesnt do anything until you cast another spell
He is in a popular color combo since you get Blue's countering and card draw, White's pinpoint and sweeping removal and Red's burn and game winners to draw into
"Well you still have to pay the mana cost, and it's instant spells only, how bad can it be?" It means you can draw lots of cards with Brainstorm, blink Chun-Li to get her out of harm's way with an Ephemerate, or make your board untouchable with a Teferi's Protection every turn