My primary source was 224 Magic Online decklists, including the first six Magic Online Challenges after the set's digital release and the Standard RC Super Qualifier, which drew in 176 players
For example, a shadow counter (produced by Minas Morgul, Dark Fortress) counts as a keyword counter because it gives the creature bearing it the shadow keyword, which means it can only block and be blocked by other creatures with shadow
They offer excellent protection during gameplay, reducing glare and wear & tear
That brings the total to 33 elder dragons as of Secrets of Strixhaven Does a Drake Count as a Dragon
Some cubes have limitations at the discretion of the designer, which includes: Standard Cubes: Cubes that only use cards currently legal in Standard
*Zellix, Sanity Flayer Haunted One, and Captain N'ghathrod are FOIL*