I can't find it out. The knives curved and magnet cant possibly do that since a knife went to his head and magnets would be a huge dissapoinetment. If I trust the devil's word and believe it isnt strings then it's probably staged and Hegla was part of it at Chapter 13
@Grikath
nah I just wanted to see something similar to https://mangadex.org/title/25495/maou-no-ore-ga-dorei-elf-wo-yome-ni-shitanda-ga-dou-medereba-ii
@Josnacio the MC will probably say that the sword girl defeated it because if they say the MC did it it would raise suspicion considering he woke up from a coma 6 months ago or something