Aliens: Dark Descent

If a marine is downed but not dead yet, basic xeno breeds will attempt to abduct them for use as hosts. You will likely get this through natural play, but if you're so good that your marines never get downed (or so bad that they die instead of going comatose ), you can force it by letting one of your marines go down and then NOT stabilizing them with a medkit right away. Let a xeno grab and start dragging them, then open fire on the xeno to kill it. Marines will automatically open fire on xenos in their line of sight, which is normally a good thing, but if you're trying to keep a xeno alive long enough to start the abduction, remember that marines will not fire when they are sprinting.