Implied Resistance to Telepathy and Mind Manipulation
Flagg regularly uses Maerlyn's Grapefruit for his own gain, as it belongs to the Crimson King and was created by Maerlyn, his (Flagg's) father. It can read the minds and memories of its users, like so.
The scans above also make it clear that the Grapefruit cannot read Flagg's memories; it only finds out that Flagg has been seeing Roland's mother by way of reading Steven Deschain's mind, heavily implying that Flagg himself was able to shield his own mind from it all this time.
Eldred Jonas touched it barehanded exactly one time in the series, but he was affected immediately.
Wizard & Glass said:
He held his hands out patiently, saying nothing, waiting for her mind to accept reality—if she let go, there was some chance. If she held on, very likely everyone in this stony, weedy yard would end up riding the handsome before long.
With a sigh of regret, she finally put the ball in his hands. At the instant it passed from her to him, an ember of pink light pulsed deep in the depths of the glass. A throb of pain drove into Jonas's head . . . and a shiver of lust coiled in his balls.
As from a great distance, he heard Depape and Reynolds cocking their pistols.
"Put those away," Jonas said.
"But—" Reynolds looked confused.
"They thought'ee was going to double-cross Rhea," the old woman said, cackling. "Good thing ye're in charge rather than them, Jonas . . . mayhap you know summat they don't."
He knew something, all right—how dangerous the smooth, glassy thing in his hands was. It could take him in a blink, if it wanted. And in a month, he would be like the witch: scrawny, raddled with sores, and too obsessed to know or care.
"Put them away!" he shouted.
Reynolds and Depape exchanged a glance, then reholstered their guns.
"There was a bag for this thing," Jonas said. "A drawstring bag laid inside the box. Get it."
"Aye," Rhea said, grinning unpleasantly at him. "But it won't keep the ball from takin ye if it wants to. Ye needn't think it will." She surveyed the other two, and her eye fixed on Reynolds. "There's a cart in my shed, and a pair of good gray goats to pull it." She spoke to Reynolds, but her eyes kept turning back to the ball, Jonas noticed . . . and now his damned eyes wanted to go there, too.
And afterwards he went from this:
Wizard & Glass said:
The ball was out of its bag and lay in Rhea's lap. "Anything?" he asked. He both hoped and dreaded to see that deep pink pulse inside it again.
"Nay. It'll speak when it needs to, though—count on it." "Then what good are you, old woman?"
"Ye'll know when the time comes," Rhea said, looking at him with arrogance (and some fear as well, he was happy to see).
Jonas spurred his horse back to the head of the little column. He had decided to take the ball from Rhea at the slightest sign of trouble. In truth, it had already inserted its strange, addicting sweetness into his head; he thought about that single pink pulse of light he'd seen far too much.
Balls, he told himself. Battlesweat's all I've got. Once this business is over, I'll be my old self again.
Nice if true, but . . .
. . . but he had, in truth, begun to wonder.
To this:
Wizard & Glass said:
He grabbed the bag just below the draw top and yanked. Rhea screamed again as the string skinned her knuckles and tore off one of her nails. Jonas hardly heard. His mind was a white explosion of exultation. For the first time in his long professional life he forgot his job, his surroundings, and the six thousand things that could get him killed on any day. He had it; he had it; by all the graves of all the gods, he had the ******* thing! Mine! he thought, and that was all. He somehow restrained the urge to open the bag and stick his head inside it, like a horse sticking its head into a bag of oats, and looped the drawstring over the pommel of his saddle twice instead. He took in a breath as deep as his lungs would allow, then expelled it. Better. A little.
Wizard & Glass said:
Rhea climbed back up, flopped onto the cantboard again with all the grace of a dying fish, and peered around at them, wall-eyed and sneering.
"I curse ye all!" she screamed. It cut through them, stilling their laughter even as the cart bounced toward the edge of the trampled clearing. "Every last one of ye! Ye . . . and ye . . . and ye!" Her crooked finger pointed last at Jonas. "Thief! Miserable thief!"
As though it was yours, Jonas marveled (although "Mine!" was the first word to occur to him, once he had taken possession of it). As though such a wonder could ever belong to a back-country reader of rooster-guts such as you.
Wizard & Glass said:
"Never mind!" Jonas shouted, pulling their attention back to him. He reached out a stealthy hand and caressed the curve at the bottom of the drawstring bag. Just touching the ball made him feel as if he could do anything, and with one hand tied behind his back, at that.
"Never mind her, and never mind them!" His eyes moved from Lengyll to Wertner to Croydon to Brian Hookey to Roy Depape. "We're close to forty men, going to join another hundred and fifty. They're three, and not one a day over sixteen. Are you afraid of three little boys?"
"No!" they cried.
"If we run on em, my cullies, what will we do?"
"KILL THEM!" The shout so loud that it sent rooks rising up into the morning sun, cawing their displeasure as they commenced the hunt for more peaceful surroundings.
Jonas was satisfied. His hand was still on the sweet curve of the ball, and he could feel it pouring strength into him. Pink strength, he thought, and grinned.
"Come on, boys. I want those tankers in the woods west of Eyebolt before the home folks light their Reap-Night Bonfire."
It can suck the minds out of people who anger it, trapping them inside of itself.
Alain states that it's sucked out either A) Roland's consciousness, or B) Roland's soul, but doesn't seem particularly sure which is closer to the truth. The next issue very much confirms it to have been the former.
Not only can Flagg touch the Grapefruit without ill effects (even after he has managed to piss it off in-story), but he proceeds to seal the demon back inside of it with no trouble whatsoever. Said demon makes it quite clear here that this was done against its will.
Also worth pointing out is the fact that Flagg, despite all of his time spent handling the Grapefruit directly, has never once been shown falling under its sway at any point. Make of that what you want, but I think it supports my case.
During his infamous final moments with Mordred, he shows that he is capable of sensing when people have breached his defenses and are reading his mind.
The Dark Tower said:
"You may wonder why I'm here, and not about your father's business," Walter said. "Do you?"
Mordred didn't, but he nodded, just the same. His stomach rumbled.
"In truth, I am about his business," Walter said, and gave his most charming smile (spoiled somewhat by the peanut butter on his teeth). He had once probably known that any statement beginning with the words In truth is almost always a lie. No more. Too old to know. Too vain to know. Too stupid to remember. But he was wary, all the same.
He could feel the child's force. In his head? Rummaging around in his head? Surely not. The thing trapped in the baby's body was powerful, but surely not that powerful.
(Important note: His general overconfidence here comes from the fact that he's currently wearing a "thinking cap" which is designed to block telepathy and psychic attacks. He placed his trust in this thing because, among other showings, it was capable of blocking his own telepathic powers when someone else was wearing it)
When he truly realizes that his mind is being read, his thoughts very much imply that he has his own innate defenses that have been breached in addition to the thinking cap's, as he compares the event to having someone break into his house.
The Dark Tower said:
There's a phrase, the elephant in the living room, which purports to describe what it's like to live with a drug addict, an alcoholic, an abuser. People outside such relationships will sometimes ask, "How could you let such a business go on for so many years? Didn't you see the elephant in the living room?" And it's so hard for anyone living in a more normal situation to understand the answer that comes closest to the truth: "I'm sorry, but it was there when I moved in. I didn't know it was an elephant ; I thought it was part of the furniture." There comes an aha -moment for some folks—the lucky ones—when they suddenly recognize the difference. And that moment came for Walter. It came too late, but not by much.
Y'won't shit on me, will you—that was the question he asked, but between the word shit and the phrase on me, he suddenly realized there was an intruder in his house … and it had been there all along. Not a baby, either; this was a gangling, slope-headed adolescent with pockmarked skin and dully curious eyes. It was perhaps the best, truest visualization Walter could have made for Mordred Deschain as he at that moment existed: a teenage housebreaker, probably high on some aerosol cleaning product.
And he had been there all the time! God, how could he not have known? The housebreaker hadn't even been hiding! He had been right out in the open, standing there against the wall, gape-mouthed and taking it all in.
His plans for bringing Mordred with him—of using him to end Roland's life (if the guards at the devar-toi couldn't do it first, that was), then killing the little bastard and taking his valuable left foot—collapsed in an instant. In the next one a new plan arose, and it was simplicity itself. Mustn't let him see that I know. One shot, that's all I can risk, and only because I must risk it. Then I run. If he's dead, fine. If not, perhaps he'll starve before—
Another final detail is that, even in his failing moments, he was able to briefly hide the fact that he had caught on to Mordred's reading of him, further implying that he can block off his mind from others. (Though Mordred's psychic abilities are too powerful for this to save him in the end)
