yugioh reflect card Duel Links 1700 Defense Fiend Reflection of the Millennium

"Oversize cards" is not a "set" by the usual Magic definition, but I'd guess your online store categorizes them that way to make it clearer to customers they're buying an abnormal card

If an attack was negated by this effect, during this turn, LIGHT monsters your opponent control cannot attack

The downside to using Cynthia is that the deck-type is very limited

Synchro and Fusion Pendulum Monsters have now also been released, but they work very much in the same way, requiring to be Synchro and Fusion Summoned first before being able to Pendulum Summon them (and some don't even allow you to Pendulum Summon them), so there is not much else you need to know about them, a Synchro Pendulum would be Nirvana High Paladin, a Fusion Pendulum would be Supreme King Z-ARC