The other 5 do not appear on the xbox 360 version or the PS3 version, and have 0% completion, which means that nobody was able to get them, just as it was with the above 5 before the release of the slingshot DLC, those are: All Aboard: Complete Confounding Light with more than 3 turns left on the timer.Rising Dragon: Take your new ally into the final challenge.The Bigger They Are: Complete Gangplank.Bait the Hook: Complete Confounding Light.New Friend: Complete Friends in Low Places.There are 10 more that don't have a description, 5 of them are related to the slingshot DLC, those are: The Volunteer: Make contact with the Ethereal hive mind.On the Shoulders of Giants: Build the Gollop Chamber.And Hell's Coming With Me: Successfully assault an Overseer UFO.Beyond the Veil: Find a soldier with the Gift.

10 of them are plot related achievements and you will unlock all of them (except from the Firestorm one) if you finish the original game: Out of the 60 achievements there are 20 that don't have a description. You can see the full list of Steam achievements at the steam site.