According to this question, the word 朦朧 is fairly common, but neither kanji is included in Ringotan. It seems neither the word nor kanji are listed as common in our dictionaries, but ロス先生 confirmed that it is. So, let's find more data sources that include this information.
Apparently JPDB lists it as common. Where do they get their information from?
A handful requested on my Patreon post, with the note: "they are mostly characters used in Buddhist texts"
蘊訶埵顛礙涅槃罜槃耨藐羯
Is there a convenient way for me to keep a list stored somewhere of kanji I've seen enough to think they aren’t rare? It looks like we can't come back and edit comments here later, which means I could end up spamming a long chain. In any case, I found another from the game: 賽, as in 賽銭 monetary donation at a shrine and 賽銭泥棒 someone who steals money out of the offering boxes.
癪 is definitely a common one!
癪に障る or 癪に触る, 癪の種, 疳癪 or 癇癪, 小癪,
JustPaste.it - Share Text & Images the Easy Way is a copy of this list Aozora Bunko Kanji Frequency List (Joyo removed) - Pastebin.com which is self-explanatory from the title - might be useful to you, of course there are a lot of alternate forms of more common kanji.
A few more I've seen multiple times:
埒、茫然、蹂躙、穢、啜、
窩、憐憫、懺悔 (I think I found this one in one Ringotan set?)、滔々
