This organization, given the hint at its lengthy history, should be massive. It should recognize XCOM as a threat and build up an appropriate response. To this end I suggest, in conjunction with previously mentioned buffs to their comm system and units in general, increasing the strength of certain variables either after each month or after each successful covert op. Randomly or simultaneously, depending on balance, increasing the following variables should help with the (lack of) difficulty getting stale: The frequency of missions against XCOM. The magnitude of these missions. The number of reinforcement waves in a covert op. The number of units in each wave. The number of pods starting on the map. I don't know how plausible it is, but would it be possible for reinforcement waves to come simultaneously from a single direction instead of scattered? I'd really like for the reinforcements to be pods of six units that enter in strategically away from the player's location. Not particularly aware of the feasibility of that but if it is at all possible it would make their reinforcements a lot deadlier.