Common cards are typically weaker than Rare cards, which are typically weaker than Super Rare cards, and so on
Cast this spell only during your declare attackers step
From what I understand, the Commander 2017 decks are doing quite well, which tells me a few things
Virtue of Loyalty fulfills this need perfectly
All players can put huge creatures and artifacts into play thanks to Braids, but cards like Cyclonic Rift and Curse of the Swine make sure that only Braids' own creatures/artifacts remain
This is by no means defined in the rules, but it is clearly against the spirit of the game to tap your Prodigal Sorcerer to deal one damage to a Knight at the start of your untap phase, then untap it and deal one more damage during that same turn