Monster Book Boss Card Costs

Well, according to the post above you, they should unlock when you're level 80, because it only unlocks on levels at multiples of 10. (Unless you were the right level at the beginning of the event.)

Not saying that that works. o_O Can't confirm it since my bishop is too high, and I'm not leveling my secondaries because of the LPQ glitch. But that's what I'm gathering from that post.