This can be very strong on its own because it means that opposing players will have to discard some of their cards if Kefka is left unattended, and the user can discard valuable combo pieces in order to later retrieve them with the Commander staple called Underworld Breach, particularly if comboed with Lion's Eye Diamond to create infinite mana and then win the game
The thing that places them so high on the list though, is that you can then pay seven mana, one of which has to White, Blue, Black, Red, and Green, to exile the top three cards of your library, and you can then play them without paying their mana costs
Vehicles laid low for the next three years, with just a small handful appearing from Throne of Eldraine to Innistrad: Crimson Vow
This offers a fun and engaging start to playing Disney Lorcana
The first three are obviously absurdly good, the Staff can be painful but well worth it if you can offset the lifeloss with Venser's lifegain