They mainly handle Pokemon Cards and MTG, along with various other trading cards
Monoblue decks ditched Jayemdae Tome completely once this bad boy came around, and started moving towards Man-o'-War and Boomerang-style board control to set up enough time for the Ophidian to give them a hand full of cards
Rift Sower Rift Sower will never be the strongest dork in the deck, but its more than serviceable
This can translate to good deals on MTG booster boxes or even booster cases (traditionally a box of 6 booster boxes, but this can vary based on the product line) in a few different ways
This often fills your graveyard and trades for a large threat, and ETBs are easily reusable with flicker and recursion abilities
You can do it at instant speed too, so if an opponent moves to destroy your creature, you can remove the counter in response