Three codes could be found in the PALACE INTRIGUE post on the Investigate Ingress blog.

[1] zlxgzaojhahsfzaazpazph

[2] w3mmy3frax9a6gm

[3] 2hqr3,s;v;byelg6f5u

Code #1

Observations

All letters, an ancient roman emperor will guide you

Code #2

Observations

15 characters with the right amount of numbers for a valid passcode

Code #3

Observations

Those special characters are a hint on what to do