Kid Icarus is a weird set, cards 1-402 have no issues and were available in normal boosters. Cards 403-412 (the Diamond cards) are special cases and were a mix of inserts, promos, and cards that weren't officially distributed. To make matters more complicated, there are three versions, European, American, and Japanese, all of which have unique distribution methods for these cards.
For Europe, we know that 403, 403, 406, 407, 409, and 412 were all printed. 403, 404, and 407 were maybe the only officially distributed ones, with 406 being difficult to find a source for. 409 and 412 exist but never had an officially official distribution, they were found in a warehouse auction. I will be able to get scans of them at some point.
405, 408, 410, and 411 have never been found in any capacity in the European set. My main question is, should they be included in the checklist, or do they need to be removed? I guess the same can be asked for 409/412 since distribution wasn't official.
I do believe they all exist since 412 was based on a Japanese-exclusive parade float, it was the weirdest one for them to print for Europe but we know they did it. If that's the case, then it stands to reason that they were all given at least very short undistributed prints.
A full rundown of European Kid Icarus Diamond Wing cards:
403: Existence confirmed, found as a hyper-rare insert.
404: Existence confirmed, found as a hyper-rare insert.
405: Existence unconfirmed, never officially released in any region.
406: Existence confirmed, no known distribution method though to my knowledge.
407: Existence confirmed, found in special boosters as a secret rare.
408: Existence unconfirmed, only officially released in Japanese.
409: Existence confirmed, a small number found in a warehouse auction.
410: Existence unconfirmed, only officially released in Japanese.
411: Existence unconfirmed, never officially released in any region.
412: Existence confirmed, a small number found in a warehouse auction.