This would drastically reduce certain elements (fire and any growth creatures) I have a feeling this will be OP because it shuts down any rush. imagine recluses doing only 3 and 2 and Phoenix doing 1.
Recluses and Minor Phoenix alike would lose 3 attack; but while Fire Spirits would hit a ceiling, Growth creatures will be hit once and then continue growing. A Lava Destroyer would be dropped to 1|1, then grow to 3|3, then 5|5, etc.
Thank you, OldTrees, for all that legwork! That's what I've grown to rely on you for, and as usual it's very helpful. I was a little scared about blowing up too many decks' star players, but apart from a few Fire creatures and a handful of others, the attack drop is pretty comparable to other shields. I think I will add a note that the attack drop happens AFTER the attack that triggers the effect - this means newly-played Ruby Dragons will get one good shot of 15 before they're crippled. Elite Pegasi will get their Dive damage, and their normal attack will remain as it is.
I realize the tendency is to look at this shield and see stuff like Ruby Dragon and Phoenix and Phase Recluse, but realize something: shields already ingame can flat-out destroy such creatures very easily. A Phase Recluse that lasts for 5 turns will equal the damage dealt by a Phase Recluse that faces a Fire Buckler... and if it lasts longer, it does even better. This shield does not block any damage.