I think the card name is "One-Winged Egret" (片翼の白鷺), actually. Maybe?
On closer inspection, the card pictured doesn't come directly after the nonspell. The nonspell's health bar has a marker for the spell following it, which doesn't match up with the health bar for Egret. That, along with the huge jump in score between the dialogue and the nonspell, indicates that this is the boss we're seeing and not a midboss. The name's probably just missing in order to avoid any major spoilers.
On some even closer (read: obsessive) inspection...
Dialogue: 10,194,080 score
14,150 point value
0/1865 graze
Nonspell: 22,860,190 score +12,666,110 since dialogue
17,450 point value +3300 since dialogue
117/2664 graze +682 graze between dialogue & start of nonspell
+1 bomb fragment (ie. only one Chapter Bonus exceeding 1 million)
Card: 29,335,330 score +6,475,140 since nonspell
20,130 point value +2680 since nonspell
146/3010 graze +200 graze between previous screenshot & start of spell
+1 bomb fragment (ie. only one Chapter Bonus exceeding 1 million)
4,391,160 left on spell bonus
I'd guess there's 2 nonspells and spells between the dialogue and the pictured nonspell (two spell bonuses, both 4~5 million since it's S4 Normal + one Chapter Bonus over a million bc bomb fragment + three sub-million Chapter Bonuses = roughly 12-and-a-half million?). So this is the third nonspell and fourth Spell Card we're looking at. I think.
The big wavy parts on the CD cover silhouette reminded me of an Eastern dragon's horns before anything else. That and the tail-looking thing on the side. It's hardly likely that we'll be fighting the Dragon God any time soon, but speaking of dragons... maybe one of the Watatsumi gods? Maybe the Watatsukis' mom??