Dead by Daylight

The fastest way to obtain this achievement is simply by playing Freddy (The Nightmare). Hitting survivors with a basic attack (or waiting 60 seconds) will put them in the Dream World. In that state, they suffer the Oblivious effect and given the extended range of this marvelous killer, you should have no problem to down 15 survivors.

For those who do not have access to Freddy, here are the other ways that a survivor can be put into the Oblivious state. Just make sure that you are using a basic attack to down them or the counter won't go up (thanks to A Seizure Salad for this information).

With perks :

- Deathbound (The Executioner teachable perk)
When a survivor heals another friend for a complete health state at least 32 meters away from you, that survivor is Oblivious for 60 seconds, but only when standing away from that healed survivor. Not the best way to go for the achievement if you're going with the Executioner (see add-on below).
- Hex: Retribution (The Deathslinger teachable perk)
When a survivor cleanse a dull totem (not an hex), he gets the Oblivious status for 35, 40 or 45 seconds, depending on the tier of the perk. This one is very situational and again, not the best way to go for the achievement.
- Nemesis (The Oni teachable perk)
Basically, when a survivor stuns you with a pallet or a locker, he gets the Oblivious status for 40, 50 or 60 seconds, depending on the tier. This one is very interesting, because you can put a survivor into Oblivious mode during a chase, when you are already actively trying to down him anyway. When you managed to injure him, stop respecting the pallet once to get the perk to activate and then go for it.
- Hex: Plaything (The Cenobite teachable perk)
When you hook a survivor for the first time, one of the dull totems left in the map will turn into a Hex and the hooked survivor will be Oblivious until said totem is destroyed. This can only apply once per survivor. This perk is great idea to get the achievement.
- Hysteria (The Nemesis teachable perk)
When you hit a healty survivor, all injured survivors will get the Oblivious effect for 30 seconds. It's not really reliable for downing somebody. Although it might get you the occasional down, I wouldn't recommend it for the achievement.

With the Demogorgon :
While a survivor is sealing a portal, he becomes Oblivious to the killer. The Demogorgon can also charge his Of The Abyss power and detect survivors at close proximity of an activated portal with the Killer instinct. Overall, not a very good way to go for the achievement either. I don't remember ever downing someone that way.

With the Twins :
When you latch onto a survivor with Victor, he will be Oblivious for the time it takes to remove the little guy (usually 8 seconds without add-on). There is an achievement for downing 10 survivors with Victor attached to them, so if you got that one, you're already at 10 out of 30.


With the Cenobite :
When a survivor picks up the Lament Configuration, he will be Oblivious until it is solved or you down them.

With add-ons :

- Lost Memories Book (The Executioner add-on)
You can find a purple add-on in the Executioner bloodweb for his Rites of Judgement power, called Lost Memories Book. When you use it, any survivor that is affected by Rites of Judgement will be Oblivious for 15 seconds. The best way to use it is obviously to try and chase the survivors towards your trail marks so they run on it and gain the status.
- Telephoto Lens (The Ghost Face add-on)
When you get revealed by a survivor while in Night Shroud, they suffer from the Oblivious effect for 60 seconds.
- Olsen's Journal (The Ghost Face add-on)
When you mark a survivor, they will get the Oblivious effect until the mark expires. In my opinion, this is one of the easiest way to get the achievement, besides playing Freddy.
- Etched Ruler (The Legion add-on)
When you hit a survivor with a Feral slash, they will suffer from Oblivious for 60 seconds.
- Drop of Perfume (The Twins add-on)
With this one, any survivor within Victor's shriek will suffer from the Oblivious status while you control Charlotte. You can also easily spot these survivors with Killer Instinct.
- NE-α Parasite (The Nemesis add-on)
When you infect a survivor, they will suffer from Oblivious for 60 seconds. It has to be the first contamination, if a survivor is already infected, he will not be Oblivious.
- Silver Bell (The Artist add-on)
Any survivor currently swarmed by Dire Crows will suffer from the Oblivious status effect. This can be somewhat useful from time to time.
- Rickety Pinwheel (The Onryo add-on)
Any survivor within 8 meters of a powered TV will suffer from Oblivious and the effect will linger for 7 seconds after leaving the area.