Creating Drained units though does make collecting 500 Essence Charges a lot easier, so another opportunity for synergy. I also suspect the Condemned to Drain tactical ability for Heritor commanders works as well, so the last mission of the Revelations campaign would also be a good place to work on this achievement, though I had already unlocked it so cannot confirm. The syndicate subjugator unit can also mind-control units, though their range is lower than the Siren's ensnare, getting the unit rather than a chrysalis might be worth the trouble. Of course if you don't have the achievement for 100 wins in manual combat then you can work on these concurrently. But I found this tactic worked well to pull out victory when at a slight statistical advantage forced manual combat rather than auto-combat. You can save before a battle to farm this if you want, if you take 6 Sirens in and have sufficient targets you'll have it after only 5 repeats. They'll run up the Siren once ensnared and then run away once impregnated.

And make sure you don't kill the units you are targeting with the Sirens with another unit's overwatch, melee or ranged. Buying the mod to increase the Siren's ability range and outfitting them with it helps as well. Two turns later the enemy unit will die when the eggs spawn leaving a chrysalis under your control. I don't remember a single time the impregnate ability was unsuccessful. Use their ensnare to draw an enemy bi-ped unit to point-blank, then use the impregnate ability on the following turn. Once they are in your army, target an enemy force with bi-ped organic enemies, and engage in manual combat. You can get these units as a rewards for faction tasks, or you can trade for them once you have a high enough relationship. My recommendation is to use Psi-fish Siren units. There are number of units, mods, and tactical abilities that allow you to take permanent control of enemy units. If you haven't completed the campaign and want to pick this up while you are it, read on for my suggestion. If you've already finished the campaign, look to Hazar's solution.

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