Throughout my past life, the highest Cadre Magivore I ever witnessed was Cadre 4.
And, even then, I was merely a Mid-Rank Knight at the periphery of battle, not one of the main characters who ended up subduing it.
I did hear rumors of a Cadre 5 Magivore, and I know it took the efforts of the entire Kingdom to finally defeat that monstrosity. I didn't get the full details of it, since the Kingdom's situation was a lot different back then than it is now, but it must have been the Thorn Overseer Vine.
It claimed the lives of millions of people.
Only thanks to the efforts of the Royal Knights, as well as the Kingdom's elite, did they manage to finally defeat the creature and bring safety back to the Randalorion Kingdom.
But, at what cost?
The Civil War… the Sarvosia Kingdom invasion… and the Magivore attack…
The Randalorion Kingdom's ruin was set in stone.
