"Kappa Cannoneer broke out in Legacy, which was definitely not our intention, and then it really was impossible to kill", he says in the above video
I can see some decks preferring this to Eternal Witness, too, which is some indication of how powerful the card is
It is fun to draw cards, and it is a lot of fun to play lower powered decks against each other without constantly worrying about someone hitting their own deck's "I win" button and landing a game-winning combo
In a similar vein to Xantcha, Sleeper Agent, this legendary creature makes an opponents creature an active detriment to their board state, and it incentivizes them to pay 3 mana to get rid of it and give the rest of the table a card
Its pretty easy to include a fair number of good Demons to the deck to make that a possibility, especially if Blood Speaker is searching them up
You must also reveal all face-down spells and permanents you control if you leave the game or if the game ends