A competitive player will deem a card valuable if its useful for deck-building, has strong/useful moves, and good synergy (aka works well) with their other cards
From the very specific card draw commanders like Matoya, Archon Elder to something more general like Niv-Mizzet, Parun, theres a card draw commander for every strategy and power level
Ashiok, Wicked Manipulator | Illustration by Raymond Swanland Yes, all past and present planeswalkers gained the Legendary supertype as of the original Ixalan
Rodolf Duskbringer Rodolf Duskbringer lets you turn your lifegain into a means of reanimation during your end step
During this phase, if your Active Pokmon has the necessary Energy attached, you may choose one of its attacks and use it
At most levels of casual play, getting back two creatures for three mana is a hell of a deal, especially given so pairs of creatures can either synergize or straight up combo