To obtain this achievement you'll first need to be playing as Zer0 and have reached level 5, as being in Decepti0n is his unique Action Skill. Now that you're playing as him, there's one Skill you're going to have to buy from your Skill Tree before you can make it last for 10 seconds or more, so this will take some levelling to reach it.

Below is the Skill you'll have to purchase;

Bloodshed Skill Tree

Many Must Fall: Killing an enemy with a melee attack while Decepti0n is active, causes you to deploy another holographic decoy, re-stealth, and add time to Decepti0ns duration. This can be done multiple times in succession.
Required Level: 30
Skill Tier: 6
Skill Upgrade: 1/1

There's also a few optional Skills worth buying that may help;

Bloodshed Skill Tree

Killing Bl0w: Massively increase melee damage against enemies with low health.
Required Level: 5
Skill Tier: 1
Skill Upgrade: 5/5

Iron Hand: Increase your melee damage and maximum health.
Required Level: 5
Skill Tier: 1
Skill Upgrade: 5/5

F0ll0wthr0ugh: Kill Skill. Killing an enemy increases your movement speed, melee damage and gun damage for a few seconds
Required Level: 15
Skill Tier: 3
Skill Upgrade: 5/5

Execute: Melee Override Skill. While Decepti0n is active and a target is under your crosshairs, dash forward a distance and preform a special melee attack, dealing massive damage.
Required Level: 15
Skill Tier: 3
Skill Upgrade: 1/1

Backstab: Your melee attacks deal bonus melee damage when hitting an enemy in the back.
Required Level: 15
Skill Tier: 3
Skill Upgrade: 5/5

Like the Wind: While moving you gain increased melee damage and gun damage.
Required Level: 25
Skill Tier: 5
Skill Upgrade: 5/5

Now that you have that, you're good to go for 10 seconds. All you need now is enough enemies to keep it going. This is easier to get playing solo because then you don't have to worry about other people stealing much need kills.