It was revealed during the 25th anniversary Tokyo Dome broadcast
Strictly for display purposes or personal enjoyment, not legal in tournaments
This can be entered at PSACARD.com and it will have a summary of information about your card, the year its from, its grade, the set its from and something even better - the POPULATION for that card
[1] These cards are rare and only a part of certain expansion sets, collection boxes, and promotional materials
Its all about counters, meaning you can buff your creatures, deal damage, and proliferate
In particular, it is possible to search for more Dragon monsters by using [Dragon Shrine] to search for more Dragon monsters after sending him GY and collecting them using [Divine Dragon Apocalypse]