For a great deal thanks to Acherontia, we can now also tame the other beasts that dont keep their visuals when they (or you) die.
I like to refer to these as the "Hardcore" beasts, since in most hardcore gametypes, when you are dead. you áre dead.
For people who still like a CHALLENGE, I have prepared this guide, for a really hard to get hardcore pet!
It takes time and effort! So you will probably want to keep him in the cities afterwords to prevent him from dieing.
So as requested, here is my guide to:
The Shadowform of the Akkarai Hatchling Owls!

Let's get started straight away!
You have to set off for Skettis, in Terrokar Forest.

Second, you are going to need 6 Pieces of Shadow Dust, from the Arrakoa all over Skettis, and turn them in at Blackwind Landing.

You will be given an "Elixir of Shadows" - Allowing you to see the spirits in Skettis.
Once taken, Go to the top of the tower, which is connected to the tower on the island.
There you will find "Talonpriest Ishaal" who drops a quest item, "Ishaal's Almanac" which is the start of a 6 parter Questchain.

These quests are not hard and explain themselves just fine. So I am skipping to the last of the 6 quests.
1. Ishaal's Almanac
2. An Ally in Lower City
3. Countdown to Doom
4. Hazzik's Bargain
5. A Shabby Disguise
6. Adversarial Blood
Now you will need to take another Elixir of Shadows, and kill spirits all over skettis (the most are in top of towers), for their "Time-Lost Scrolls"

You need 10 of these Scrolls, then you move on to one of the Skull piles, there are quite some spread all over skettis, you should have noticed them farming the scrolls.
Before you use them, you might want to clear a bit of the area around it.
Here you will choose to call forth Darkscreecher Akkarai.

Our friend Darkscreecher Akkarai is the one who is going to summon our new best friend.
He has alot of stamina, so just kill him slowly, and be sure to have at least 4 or 5 of his summoned birds on you before you finish him off.

These birds will not fade away untill they are out of combat. And they do not do alot of damage, so you can slowly try the taming process on each of them.
They can only be tamed with their visual effect with the following macro:
(This macro was created by Acherontia. Thanks Brah <3)

You have to spam that macro like you mean it, when the taming is almost done, untill a little bit after when you are sure the owl is gone.
You will probably not fail a single time. I would advise to succesfully tame more then one, since the effect wears off on death, and you probably dont want do go farming scrolls here agian.
That was my guide for today!
Happy Hunting all!
~ Griffley - Ravenholdt EU