Theres a pretty significant value jump between Fourth and Alternate Fourth for some of the collectors who do know about it, so it may be worth your time to double check none of these cards are in your collection
Legality depends on the tournament format -- Katilda, Dawnhart Martyr // Katilda's Rising Dawn can be legal in some formats and banned or restricted in others
One-sided board wipes are incredibly powerful, and its often worth the extra two mana to keep your Creature alive
Progenitus used to see play in some Natural Order decks and even in Commander decks, but there are way better alternatives at the 10-mana value range and in five colors these days
The game system is based on resource management, using ink as currency to play cards and activate abilities
The idea is that in a 100-card format, the math to simulate having four-of a card results in you running seven cards of the same functionality