Here is the full list of all 20 Tentacles: Enter the Mind achievements worth 200 gamerscore.
You killed a Rammstein without using any powers!
Nice, you killed 5 enemies with one bomb!
Wonderful, now Dr. Phluff has no regrets!
You cracked a black egg!
You were the target of five snipers at once!
Great, you used all of your powers!
Wow, a Kamikaze orbited you!
You reached a multiplier of 10!
You equipped the rainbow trail and the pink eye.
You cracked a purple egg!
You completed the Libido Layer!
You just bought yourself some more time!
You grabbed the oscilator really tight
You reached a multiplier of 8!
You found the loophole in the knife
You selectively killed Kamikazes without killing any other creatures!
You picked up 3 tombstones without dying.
You held three rubber duckies at once!
You cracked your first egg!
You went from one pitstop to the next without killing any enemies!