I got this achievement yesterday, and the difficulty is that it is relatively random. However, I'll share my anecdotal advice.
First, hit all the shops you can. Shops don't always have crew, but there's a chance that they might. I've found that shops in a sector belonging to a particular race tend to have that race more often, but it's random - sometimes I've been in Engi space and seen a shop full of Zoltans, for instance. Crewmembers tend to cost less than 100 scrap, but I'd suggest trying to have ~100-150 scrap on hand just in case you find a shop that's got 2 races you need.
One event that I believe is more common in "pirate" and "civilian" sectors is an encounter with a slaver. They may attempt to extort you to give them either some scrap or one of your crew members. If you fight instead, they may later attempt to surrender by offering you a crew member.
From time to time when fighting a ship and killing its crew, I've been told it was a prisoner transport ship and that one of the prisoners wanted to join me. I'd suggest attempting to take ships intact for this reason. I haven't seen any indications in the initial system event that would indicate whether a ship is likely to give a crewmember if taken intact, though.
There are also events where you find a lone survivor on a deserted station, and this can sometimes provide you with an additional crewmember. However, there's also a chance that they will go crazy and murder one of your existing crew, so this is not always a reliable way to make progress towards this achievement. Commenters have noted that having a level 2 medbay can counter this, as can a slug crewmember.
From this page:
Humans comprise the majority of both the Galactic Federation and the Rebel Fleet. Humans learn skills faster due to their reduced XP ability, have no notable weaknesses and are the cheapest race to hire from Stores.
- Skills improve slightly faster (10%)
Engi originate from the Engi Homeworld. They take 50 to hire, with the following special traits:
- Repair speed is doubled
- Combat damage is halved
The Mantis originate from the Mantis Homeworld. It takes 45 to hire them.
- Inflict 1.5x damage in combat
- 1.2x move speed
- Halved repair speed
Rockmen are strong creatures and take 65 to hire. Their abilites are:
- Immune to fire
- Movement speed is halved
- Health is increased to 150%
Zoltan usually appear in Engi Homeworlds or Engi-Controlled Worlds. They appear rarely, and it takes 65 to hire them. Their special abilities are:
- Provides (1) power to occupied system
- Health is 70
- Explode when killed, damaging all enemy crew in the room
Slugs are one of the rarest crew to find. Their advantage is the ability to see your enemy's crew, and to be able to see the rooms surrounding the slug in your ship if your sensor goes down. They cost 45 to hire.
- Telepathic powers reveal rooms and lifeforms even when sensors are down.
The Lanius are scavengers – metallic lifeforms that rely on the absorption of minerals to sustain themselves. They are available only in advanced edition and even then are almost exclusively found in the Abandoned Sector where they cost 50 to hire. They need no oxygen and also drain oxygen from the room they are in.
- Drains oxygen from rooms
- -20% movement speed
- No damage from suffocation
And a final 'secret' race:
Crystals can be found in Life support pods that are revived by scientists. Doing so also begins a special quest to the Rock Homeworlds.
- Lockdown power: When finished charging, sends crystals to surround the room they are in, making it completly invincible to damage (Only that specific room). Nothing can exit/enter the specific room until the ability wears off.
- Reduced suffocation damage
- Movement speed -20%
- Health 125
Best Answer
It means the crew has been stunned. The effects are only temporary though.