Hamms dark, detailed, and creepy phantasmagoria is Innistrad , for me, with the original Delver of Secrets, Dungeon Geists, and later Skin Invasion, to name a few
Speed comes from consistency in the first three turns, so having a high volume of these creatures provides the damage these decks want
Especially since Phyresis Outbreak gives each opponent a Poison Counter to start with
However, as is the generally the case with Pokmon Search Supporter cards, because the player going first cannot play a Supporter card, its likely that Item-based search options will be preferable to this card and other cards like it
The card is a bit clunkily worded, but in essence, it basically splits each player's creatures into two sides of the battlefield (or the "river")