Its an excellent card to pull from this set, so keep it safe if you have one
This is at its best in stax decks leveraging cheap creatures like Collector Ouphe and Archon of Emeria or token decks building out massive numbers of 1/1s
In practice, however, these are often desired prices that are never actually achieved
This means Arceus has to rely again on other teammates, which changes the style of playing this deck
Once transformed, it becomes Polukranos, Engine of Ruin, which is a 6/6 with reach and lifelink and reads: Whenever Polukranos, Engine of Ruin or another nontoken Hydra you control dies, create a 3/3 green and white Phyrexian Hydra creature token with reach and a 3/3 green and white Phyrexian Hydra creature token with lifelink. Even without any other hydra creatures, the fact this card will split into two is amazing - but with some clever deckbuilding, it could make your deck unkillable
This creature has two abilities, and those two abilities are super powerful when working together