Bladed legacy?

[excderin-ex]

How do I get this stage?

[EspioKaos]

Dagora City Flyer Base > Valley of Carnage > Mine Defense > Lonely Laboratory

After clearing Mine Defense, you'll come out into a large cavernous lobby. There are multiple mission counters here, so it might take a moment to find the one that leads to Lonely Laboratory. But once you clear that mission, you'll come out at Il Cabo Base which is where you can start Bladed Legacy.

[EspioKaos]

Is it IL Cabo Base or 2 Cabo Base?

It's I-L. Like "ill" minus the second L.