Not a single instant or sorcery
If that wasn't amazing enough, if your opponent removes Chaos Archfiend from the field in any way, it allows you to Special Summon a Chaos Synchro monster from your Extra Deck, giving you quick access to cards like Chaos Angel and Chaos King Archfiend
Originally, they were released in March 2003
Im sure many people will still bemoan the fact that it isnt on a console (as its predecessor was), but TCG Online is, in all honestly, probably better than a retail followup could have ever been, which makes this complaint a moot point (I very much doubt a 3DS version would allow you to import your real purchases into the game, let alone be flexible enough to update each time a new expansion is released)
Even in entries into the franchise where crystals were not central to the central plot, crystals are at least referenced, underscoring their importance to the Final Fantasy universe's overall lore