Go to trading post, then click to undercity and the way to vivarium you can find on the right side of your screen
make sure to use lacerate->firearms->defend mechas in this order for chance to get combos (you most likely know that already, but i am just making sure). remember that the more power that you have in your bag the stronger the combos' damage. also, the more points that you have in the alf tree the higher the chance for the robots to crit. make sure that you have enough ammo and medkits. with the alf's playstyle you mainly need to wait for the regroup drone to crit enough so that he will raise the crit rate of your mechas and you get combos all the time.
