(Fusion/Ritual Monsters) Fusion monsters can only be played by fusing 2 or more monsters together with a Magic card that has the effect to do so (like polymerization)
Which is why, despite all the talk of big money in Pokmon these days, a lot of the biggest transactions are completely free
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
Finally, staying informed enhances long-term enjoyment
As a winning snapshot from the contest, this card showcases the awe-inspiring might of Gyarados