Here is the full list of all 20 Tentacles: Enter the Mind achievements worth 200 gamerscore.
Fly through the hole of any knife.
Go from one pitstop to the next without killing any enemies.
Hold on to three rubber duckies at once.
Pick up 3 tombstones without dying.
Have a Kamikaze orbit Lemmy
Get 5 snipers to aim at you simultaneously.
Crack your first egg.
Complete the Libido Layer.
Use a revive token.
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.
Kill 10 Kamikazes without killing any other creatures.
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.