Have anyone wondered what does blue rose means in Ragna crimson??

Ragna crimson volume 3 cover

Ragna crimson chapter 93

Ragan crimson ch55 (manga)/ep24 (anime)

This blue rose appeared each time the dragon god shows up... + volume 3 cover with ultimatia holding it, i guess it must have some special meaning.. What are your thoughts on this? (!! spoilers for those who haven't read the latest chapter!!)