FAIR IN LOVE AND WAR - AND UP TO DRUGGING

Lady Valdis (who looks a-do-ra-ble in this panel!) is up to drugging Markus to get his ex-girlfriend's gown, even though she may cause his death with that draught of hers:

In my EAH fic, Katla (Valdis's daughter by her latest consort) uses the same tactics to subjugate Charles (descendant of Alice), her first crush. At the first drink, he is instantly half-conscious ("now the room's reeling... now the room's foggy... the light goes out..."). Over time, he develops an addiction to Katla's drug and his personality changes to much a more withdrawn one... as Katla doubts that Charles may not be the one she actually loves... but his health is also gradually declining, and he is each day nearer to dying of poisoning!

In Edith Pattou's novel, the drug used on the dashing and golden-haired Charles by his troll fiancée is a powder called rauha. Which happens, coincidentally, to be the Finnish word for peace (cognate with German "Ruhe". Many troll words in the novel are actually Finnish)! It's used, in the first place, as a painkiller, with the side effects of erasing the drinker's memories and creating a strong addiction, and withdrawal from rauha is lethal to addicts (could rauha actually be opium/laudanum? Or some mushroom substance, perhaps? I think it's most likely to be deadly nightshade, or some other alkaloid!)...

Charles
Nyamh
Ice Queen

    It was a man.

      His hair was golden, glowing bright as a bonfire in the light of the candle. And his features were fair. The stranger was wearing the white nightshirt. It fit him well, not too wide nor too narrow across the shoulders; the sleeves falling to his wrists, neither too long nor too short.  

He lay on his side. His hand curled gently on the white sheet in front of him. There was a silver ring on his smallest finger. I could see sparse golden hairs on the back of his hand, and the curved fingers seemed vulnerable.

I made sure that Urda and Tuki wrapped him well in furs and gave him frequent draughts of slank. The cold will be an adjustment for him, but soon enough he will grow used to it.

His lovely face is pale and pinched with unhappiness, but it does not disturb me, for in time that will fade. There is rauha in the slank and this will help ease his pain, and blur his memories as well.

And my queen is most generous when the nightmares come. If I cry out, which I often do, she will come to me at once and bring me a cup of warm slank. She sits with me until my shaking abates.

 I do not think there is anything now that would stir Myk's memory—the rauha slank is too powerful for that to happen—but such a slip-up may trigger a nightmare. (I still do not know why the slank does not eliminate those occasional nightmares. It is irksome.)

      I saw Tuki for just a moment that afternoon, and he whispered to me, when no one was near, that he had given Myk the unpowdered slank again the night before. It had been seven days since the white bear's last dose of slank laced with rauha. Tuki saw a difference in him.

Tuki learned that Myk had a large cup of slank each night before bedtime. For a week Tuki had managed to substitute plain slank for the kind with the powder. I have some idea he switched his own slank, unpowdered, for Myk's, which he poured away. 

   I have been feeling somewhat odd of late. Not ill or unhappy. Just a little different, like my sight is clearer, or my thoughts. Or perhaps it is that I feel more awake; I certainly rise in the morning feeling more alert. I can't quite figure it out, but I am glad of it.

       I have even had brief memories of the time before I came to the ice palace. Even before I became a white bear. They are fleeting but pleasant.

      Just today I recalled being a child and playing on a field of the greenest grass, with many bright yellow flowers poking through the green. There were other children and we were all laughing together at something. It was very enjoyable, the memory.

      I have not told my queen because she does not care for mention of the past. And I do not wish to upset her, especially when she is so busy preparing for our future happiness.

Myk seems sleepy eyed, somewhat subdued. I suppose it is the effect of the double portion of powdered slank I gave him last night. But when he looks at me, he smiles...

  Last night Myk had one of his nightmares, the first in some time. I attribute it to wedding-night jitters and am not unduly concerned. He was very agitated, though, and I had to give him double the portion of the powdered slank. It was very peaceful, holding him in my arms as he settled down to sleep, his golden head resting on my shoulder.

    MY QUEEN IS RADIANT. I can hardly believe it is me she wishes to wed. Tomorrow. How can I be worthy of such an honor?

      Tuki is acting odd. All the time he gazes at the entrance, as though expecting someone to enter. He has hardly touched the delicious food.

      I wish I did not feel so drowsy and dull witted.

...but most died because of the slank—or, I should say, of withdrawal from the slank doctored with rauha. Those who had been at the palace for years and had been fed a daily diet of it were not able to adjust to life without slank. The withdrawal was a terrible thing, causing a violent trembling of the entire body, vomiting, and eventually an abrupt halt of breathing.

  "Charles," he replied.

      "My name," he said with a smile that lit his face. Setting down his flauto, he leaned over and picked up the book beside him on the couch. Opening it to one of the blank pages at the beginning, he pointed to some words written in a flowing, cursive hand:

       Charles Pierre Philippe, Dauphin

      "I wrote this," he said. "My name. I am Charles Pierre Philippe." He set down the book.

      And then he took both my hands tightly in his.

CHARLES PIERRE PHILIPPE was the fifth child of Charles VI, king of Fransk. My friend Havamal, the custodian of Master Eckstrom's library of books, helped me track down information about Charles's origins. It turned out that Valois, the word inscribed on the ring he gave Rose when they married, was the title of the line of royalty from which he was descended. Charles's younger brother was the dauphin whom the maid Jeanne d'Arc helped to put on the throne. But that is another tale.

      All it says in the written history was that Charles, beloved son of Charles VI and Isabeau, was born around the time of a peace parley of Amiens and died at age nine. From what we have learned of his parents—his father was hopelessly mad and his mother greedy and traitorous—it is possible he was better off as a white bear. I do not know whether he would agree with that or not.

       Charles dedicated himself to music and, in fact, invented a new design for flautos in which the mouthpiece cap contained a sponge to absorb the moisture from the player's breath. It was quite a success, and Charles became both a sought-after musician and an inventor. However, he never cared much for traveling, preferring to stay at home with his wife and children. They had four—one for each of the cardinal points of the compass.

In TV Tropes:

Yandere: When the Troll Queen takes Charles back to her kingdom after he becomes human permanently, she immediately starts drugging him in order to make him forget his time as the white bear and fall in love with her.

• Charles, when he was still a pampered dauphin, was quite happy to play with a completely strange girl and apologised to her immediately after saying her voice was odd. No wonder said girl, who grew up to be the Troll Queen, fell for him seriously.

In the Laboulaye story Perlino (rather influenced by Andersen's Snow Queen!), the leading character, blond and dashing like Charles, is tricked by the Countess of Clanking Shields to drink a golden powder that freezes his heart to ice, making him care for nothing but the poisonous powder, and causes addiction.