As a "pure" deck, Horus turbos out a ton of beatsticks with high ATK and that are notoriously hard to remove without the opponent being severely punished
On the other side, many green decks are built around Llanowar Elves and Badgermole Cub, using their accelerated mana production to deploy powerful threats ahead of schedule
He gives various lectures to the protagonist, and he can also duel
(Maggot Therapy can be used this way as an instant, once youre pretty sure Massacre will resolve.) Maybe you could put a Sadistic Glee on something like a Negator or Delraich
You can swing for five damage with Hateflayer on any given turn and then pay three to put another five wither damage on any target
Although the card is today very valuable, when it was first printed (over two decades ago) nobody had any idea that it would one day be so valuable