IPA: /ˈmɪstɪfaɪŋli/
KK: /mɪsˈtɪfaɪŋli/
In a manner that causes confusion or puzzlement.
The magician performed mystifyingly, leaving the audience in awe.
Mystifyingly → It is formed from "mystify" (from Greek "mystikos", meaning secret or hidden) and the adverbial suffix "-ingly" (meaning in a manner of). The word "mystifyingly" means in a manner that causes confusion or wonder, often due to something being secretive or hidden.
Think of something that is 'hidden' or 'secret' ('mystify') and how it can be done 'in a manner' ('-ingly') that confuses or amazes you.