Here is the full list of all 20 Tentacles: Enter the Mind achievements worth 200 gamerscore.
You went from one pitstop to the next without killing any enemies!
Wow, a Kamikaze orbited you!
You picked up 3 tombstones without dying.
You held three rubber duckies at once!
You just bought yourself some more time!
You selectively killed Kamikazes without killing any other creatures!
Fly through the hole of any knife.
Get 5 snipers to aim at you simultaneously.
Crack your first egg.
Complete the Libido Layer.
Attach all three tentacles to the oscillator screen on the science box
Use all 3 powers.
Equip the rainbow trail and the pink eye.
Kill 5 enemies with 1 bomb.
Crack a purple egg.
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.