Espionage in game

  Special skill tree (or simply imperial service as in civilization for example) that contains various actions from simple to complex:

  For example, at the beginning there is a small sabotage, which reduces food production by a certain number (or %) in a few turns, steal vision, obtaining intelligence.

  Further, such actions as assasination of the governor, copying of technologies, depopulation due to massive sabotage or giant terrorist attack, destruction of system improvements, production of ships/improvements in enemy's system for part of its FIDS and secretly delivering them to another system.

  Various provocations in the diplomatic sphere and domestic policy: dissolution of trade or research agreements, alliances, peace treaties, SUDDEN declaration of war, tampering with voting results, lowering approval level.

Also such methods of countering espionage as police/counterintelligence (system improvements) or skills in Universal/Espionage skill tree, like in Endless Legend.

Spy implementation methods are also similar to Endless Legend.

Not native english speaker, apologize for possible errors.