Here is the full list of all 20 Tentacles: Enter the Mind (Windows) achievements worth 200 gamerscore.
You completed the Libido Layer!
You picked up 3 tombstones without dying.
You cracked a purple egg!
You selectively killed Kamikazes without killing any other creatures!
Sweet, you found the knife loophole!
You grabbed the oscilator really tight
You cracked your first egg!
You went from one pitstop to the next without killing any enemies!
You held three rubber duckies at once!
You just bought yourself some more time!
Have a Kamikaze orbit Lemmy
Get 5 snipers to aim at you simultaneously.
Use all 3 powers.
Equip the rainbow trail and the pink eye.
Kill 5 enemies with 1 bomb.
Crack a black egg.
Kill a Rammstein without using any powers.
Complete the entire Regret Layer.
Reach a multiplier of 8.
Reach a multiplier of 10.