This achievement is earned by using the biotic "Stasis" ability 75 times. It can be earned very early in the game; in fact, I got it on the first mission to Eden Prime, without reloading.
Start by creating a character and select the Adept (pure biotic) class. After the introductory cutscene, pull up the menu by pressing start. Select "Squad" and put two points into the Barrier talent. Where you put the other one is up to you. Exit the menu by pressing B (
The next thing to do is explore the entirety of the Normandy (the ship you're on), examining everything and talking to everyone, to earn as much XP as you can before the mission starts. Leave talking with Nihlus for last so you don't miss anything.
Then begin the mission, and again, examine everything as you go. You'll get into a couple fights as you make your way to the dig site, likely gaining a level on the way. On the right side of the dig site is a ramp leading up towards some buildings and your first encounter with husks. If you haven't missed anything along the way, adding husks to your codex should give you just
enough XP to hit third level, right as combat starts.Immediately
(before fighting them!) turn around and run back down the ramp (hold A (
) to run). At the bottom, there are two openings in the wall to the dig site. Right about where the second opening starts, there is an invisible boundary between zones—cross this and you will be out of combat, and the husks will disappear
Now that you have a moment of free time, press start to call up the menu again, then spend your fresh new talent points into the third and fourth slots of Barrier to unlock the Stasis talent, and put a point or two into Stasis. Exit out of the menu.
Hold RB (
) to call up the power wheel. Highlight the shiny new Stasis power in the Shepard section and press X (
) to map it to the RB (
Look toward the far side of the dig site and hit up on the D-pad (
) to command your team to move there, where they'll be out of the way and won't kill your toy husk. Now all the preparation is out of the way and you're good to go.
Creep forward until you've crossed the invisible line and the husks reappear, either in front of you (if they chased you down the ramp) or up the ramp. When one is in sight and within range, target it and tap RB (
) to put it into Stasis. Then take a step backward, across the boundary, and the husks will vanish again.
Wait for your power to refresh (about 60 seconds at this low level; you can check by holding RB (
) to bring up the power wheel again). When it's ready, creep forward again and the husks will reappear. And what do you see? The one you put into stasis is still
in stasis! While it was vanished, its timer wasn't counting down!
You can now cast Stasis on it again, even without waiting for the previous stasis to wear off. If the other husks have made it to the bottom of the ramp, it should take them a second or two after appearing to turn around and find you—but by then, you can have already stepped back and made them vanish again. Or you could target a second husk for your next Stasis, or let your team kill them off. Anything in stasis will be unable to move or act, so they cannot attack; they also cannot be attacked, so your target husk should be safe from your team until you back up.
In this way, you can keep the husks in stasis perpetually, and any others will be disoriented every time they reappear. After doing this 75 times, your achievement should pop.