If, like me, you consider this more of a Wrath effect then it looks insane
That Special Summoned monster's ATK becomes doubled, also it cannot be destroyed by battle, except by battle with a "Number" monster, nor by card effects
Once its engine starts, Hashaton floods the board with undead copies that snowball into an unstoppable, shambling army
You can cast Failure to bounce a spell and then Comply naming the spell, and your opponent can't cast it on their next turn, but Reflector Mage (an uncommon itself upgraded from common thanks to the "can't cast" clause) comes along with a very blinkable and close to on-curve body, which makes it much, much better than Failure // Comply
After damage calculation, when this card is destroyed by battle with an opponent's monster: Banish that monster, also banish this card