These all give you access to powerful removal, counterspell, and protection, something very much appreciated in a deck like Calvary Charge that wants a lot of creatures on the battlefield on your side and little on your opponents'
Sign in Blood can also become an expensive Shock to close the game out
Its pretty common to play this on turn three before you play your land for the turn to ensure it works, and it can contribute a fair bit of damage in the early turns, too
If you wana make good blockers use war marshal, epochrasite, Cathar, courser,, thragtusk, voice, blade spliced as your model and try to find a way to privilege defense in a novel way so they don't just end up lining the pockets of 2/1 decks
Anguished Unmaking Anguished Unmaking is more premier removal for Commander that hits many more types of cards
1 Foil-etched Display Commander