Shade of the evening
From A Wiki of Ice and Fire
It is a sorcerous drink drunk by those who enter the House of the Undying and the warlocks of Qarth, so that they may "hear and see the truths" that will be laid before them. It does not turn lips blue with just one dose; many must be taken.
It smells like rotted flesh and has a thick oily texture and tastes like all the tastes a person has ever tasted, and some that a person hasn't.  To Victarion Greyjoy it looks like strange black wine that flows as thick as honey when poured.  When he sees it up close it looks more blue than black. Travelling warlocks have been known to take a cask of shade of the evening with them.
There is a potent magical elixir made of virgin’s milk and shade of the evening sold at the Port of Qarth, the name of the elixir is not mentioned.
Those known to drink shade of the evening
- Pyat Pree
- Daenerys Targaryen (only once)
- Euron Greyjoy
- Victarion Greyjoy – tries a small swallow and spits it out immediately. 
A Clash of Kings
In Qarth, when Pyat Pree and Daenerys reach the door to the entrance of the House of the Undying the smallest dwarf Daenerys has ever seen is waiting on the threshold. He stands no higher than her knee, his face is pinched and pointed, snoutish, but he is dressed in delicate livery of purple and blue, and his tiny pink hands hold a silver tray. Upon it rests a slender crystal glass filled with thick blue liquid: shade of the evening, the wine of warlocks. When Daenerys asks if the wine will turn her lips blue Pyat Pree answers:
|“||One flute will serve only to unstop your ears and dissolve the caul from off your eyes, so that you may hear and see the truths that will be laid before you.||”|
The first sip tastes like ink and spoiled meat, foul, but when she swallows it seems to come to life within her. She can feel tendrils spreading through her chest, like fingers of fire coiling around her heart, and on her tongue is a taste like honey and anise and cream, like mother’s milk, and Drogo’s seed, like red meat and hot blood and molten gold. It is all the tastes she had ever known, and none of them … and then the glass is empty. 
A Feast for Crows
Euron Greyjoy came across four warlocks (one of whom may be Pyat Pree} when he captured a certain galleas out of Qarth. They had with them a cask of shade-of-the-evening which he claims as his own ang begins drinking from it.
Later, in Lord Hewett's bedchamber, Euron Greyjoy pours two cups of shade-of-the-evening and offers one to his brother Victarion Greyjoy. Victarion takes a small sip and rejects it. Euron drinks deeply from his own cup, and smiles.
|“||“Foul stuff.” ||”|