With blank cards you can test out expensive cards like Sheoldred, the Apocalypse and Snapcaster Mage to see if they work in your deck before committing to buying them
Bonus points if you blink her at instant speed after combat to reset the trigger
Kelsinko Ranger can buff Green creatures
Another thing to note is that cards that usually work well in hydra decks are green based, so there arent a lot of incentives to run other colors except to splash a Simic, Gruul, or Golgari hydra
you can play cards from the top of your deck with Falco Spara, PactweaverFalco Spara, Pactweaver, draw cards from The SwarmlordThe Swarmlord, make huge Hydras with Zaxara, the ExemplaryZaxara, the Exemplary, or dea damage with Shalai and HallarShalai and Hallar
The cards in Beta were different from Alpha due to different printing technologies being used