An opponent might get out a first turn Jackal Pup, follow it with a second turn Dauthi Horror, and cap those off with a Mogg Fanatic and Dauthi Slayer on turn three, but your third turn Propaganda would ensure that you didn't take a full seven damage to the noggin on turn four
Summon: Knights of the Round is a saga card with five stages that trigger after each turn
Now this bad boy is based on the absolutely busted Library of Alexandria while our wizard friend isn't quite as busted he still is very strong filling two rolls at once
It also nullifies your opponent's graveyard - pretty backbreaking for strategies like 'Dredge' that rely on the 'yard - and allows you to grab your opponent's best threat from the void and play it free of charge (Okay, at the cost of its own life, but it's a lowly two-drop, so who cares?) Paired with targeted discard cards like the popular Thoughtseize, Dauthi Voidwalker has the potential to be super scary
Adamant If at least three blue mana was spent to cast this spell, scry 3