Nimbus is bummed about the outcome of the last mission—they were really rooting for you. They sympathize by recounting Rohan's little catchphrase for such an occasion: "Headlong and empty-handed," explaining that it's okay to stop trying to do it all yourself; we're in this together. We'll fix this.
Whatever the Witness wants from the Veil clearly involves using the Radial Mast to create some sort of… link? So the threat remains high. But right now, the CloudArk—Neomuna's virtual infrastructure built on the Veil's power—needs our help. "I'm sure you've seen the virtual citizens milling about the city. You see… nah, you know what, I'll explain details on the way. Point is, to protect the Veil, we need to protect the CloudArk." Your direct assault on Calus failed. Time to try a different approach.
Nimbus recommends you check in with Rohan and Osiris at the Hall of Heroes before moving on to mission "Breakneck."