Here is the full list of all 20 Tentacles: Enter the Mind achievements worth 200 gamerscore.
You held three rubber duckies at once!
You cracked your first egg!
You went from one pitstop to the next without killing any enemies!
Fly through the hole of any knife.
Pick up 3 tombstones without dying.
Have a Kamikaze orbit Lemmy
Get 5 snipers to aim at you simultaneously.
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.