Arcbound Worker Ah, the classic worker peon
Giving flying to your whole team is incredibly strong, which is why it comes on such a relatively weak 6-drop
They are intended to make playing with the new cards more fun by clearing up the common misconceptions and confusion inevitably caused by new mechanics and interactions
Simply playing an over-statted 3-mana creature that draws cards when it attacks poses enough of a threat to make this an excellent Cube card regardless of graveyard synergies
I personally play a minimum of 6 cards and a rough maximum of 10, with the caveat that commanders like Lord Windgrace are going to require more than commanders like Kinnan, Bonder Prodigy
Teferi's is whispy to show his time-manipulating skills, Chandra's are singed for her pyromancy, Garruk's have plants growing in the background, and so on