The natural scarcity of the Aquapolis set, combined with its age, has made it a very desirable set in the modern age of Pokmon TCG collecting, and just like most releases from that decade, it's considered one of the holy grails in the collectibles space at the moment
It also gives you some incentive to keep Grimer around until a big Pokmon shows up, but this might cause Muk to come in with less health than is normally ideal
006 - Destroyed 30 of your opponent's monsters in battle during a duel
Meanwhile, the Temur respect the forces of nature, and call upon the fierceness of the wild for their protection
Other cards that help get essential cards on the field are Pok Ball for finding basic Pokmon, Professor's Research for drawing cards, and X Speed for switching out what is in your active spot