There are 2 secret achievements in Combolands
NB: This info is as true as I know based on what I did vs what didn’t work.
Spoilers ahead!
Bribery and Corruption is unlocked by unlocking the Rogue Guild.
This is done by unlocking the Spymaster, which is offered as a Milestone challenge at times. After once Council vote from the Spymaster, they can show up as a vote and add Rogue buildings to the pool. Finishing a run (pre-endless) after this unlocks the guild.
Hidden Enchantment is unlocked by unlocking the Arcane Guild.
This is done by getting a Gemstone Satchel – easiest to get it via the Anitquarian – fill it with gems, then sell it. You get a crown, which, if sold, gives you a Wizard vote. This unlocks their vote permanently and adds Arcane to the pool. Finishing a run (pre-endless) unlocks this guild.
Unlocked doesn’t mean you get to pick them at the start, they just show up on the end screen.
I found Civic and Commercial to be great for these – got them both in one run. You need to generate a fair few coins for the Spy, and it also helps in re-rolling shops for Antiquarian votes and finding Gems.