It means you can kill creatures as long as you have mana
In addition, a wide variety of cards will return as Rares, but since this is Maximum Gold, theyll be appearing as Rares with gold lettering instead of the standard silver
Both have their perks, and I faced two of them during the rounds that were using the Land Form Shaymin, and killing even Weedles was hard as they had 90 HP
Theres also plenty of ramping options, such as [scryfall]Farhaven Elf[/scryfall], [scryfall]Wood Elves[/scryfall] or [scryfall]Fertilid[/scryfall], not to mention all sorts of bullets, such as [scryfall]Scavenging Ooze[/scryfall], [scryfall]Reclamation Sage[/scryfall], [scryfall]Loaming Shaman[/scryfall], or [scryfall]Selkie Hedge-Mage[/scryfall]