- "I am a mangy vagrant. Gaunter O'Dimm, at your service"
- —Gaunter O'Dimm
Later during the Epilogue in White Orchard, in one of sidequests, one of the five dwarves from the Isle of Mists mention O'Dimm as "Mr. Mirrory", the recipient of a chalice they had lifted from former Lord Dagborg.
- "All who have learned my true name are now either dead or have met an even worse fate."
- —Gaunter O'Dimm
Gaunter O'Dimm's true identity remains a mystery throughout most of the game, with Geralt becoming increasingly suspicious of the true nature of this "man", who demonstrates the ability to steal souls, grant wishes, see things for their true nature, and manipulate time itself. O'Dimm refuses to reveal his true name to Geralt, warning that those who learned it suffered a terrible fate. Through talking to people Geralt learns that O'Dimm will happily make a deal, either written or oral, with anyone who asks.
The catch is that the deal is filled with conditions and wordplay loopholes through which O'Dimm can claim payment, apparently often Faustian in nature. The clearest example of this trickery is shown with one Professor Premethine Shakeslock: O'Dimm granted him physical protection but forced him to remain within a spell diagram, caused mental damage with dreams and visions, finishing with setting a trap to kill Shakeslock should he ever leave it.
Geralt, thanks to Shani's help, eventually finds professor in city where he has cloistered himself in his house out of fear of what he has discovered. He tells witcher that Olgierd had hired him to research O'Dimm's identity and discover how Olgierd might get rid of him. He "pored over countless tomes, delved into obscure incidents and analyzed folk legends", and came to believe that, in short, O'Dimm is "Evil Incarnate".
O'Dimm is just one of many names belonging to the entity, a record of whose presence could be traced throughout millennia and across different cultures, and is a being who appears to relish meddling in human affairs, their souls, and sowing misfortune.
The professor reveals that simply studying about O'Dimm had caused him to go blind which had in turn attracted the attention of O'Dimm himself and had drawn the professor a magical circle of protection as a reward of sorts, telling him that he would be safe as long as he remained in the circle. However he then made the celling brace above the circle weaken, creating a death trap for the professor should he leave the circle. Geralt managed to get the information he wanted out of the professor who proclaimed that he felt happy just to be useful again. This reaction corresponded to the failure of the celling brace, causing structural damage and shaking the walls with enough force to cause a bookcase to fall. Geralt managed to hold the bookcase upright but the professor tripped over a bottle as he backed away, causing him to fall outside the circle and to break his neck on a small pile of books, instantly killing him.
In exchange for his past aid, O'Dimm has contracted Geralt into helping him finish up a different contract: to grant three wishes of the immortal Olgierd; telling him once the wishes have been granted he will free Geralt of his pact.
Through the tasks Olgierd makes him do, Geralt learns that Olgierd had previously made a pact with O'Dimm for the restoration of his wealth and power so that he could once again be nobility and marry his noble-born love, however it was shown that as a "side effect" of his fulfilled desires, Olgierd had developed a heart of stone: losing his capacity for any emotions over time, culminating in the eventual death of his wife.
Geralt encounters O'Dimm again at a tavern where he is stopped by a drunk patron inviting him to drink, causing O'Dimm to lose patience and stop time itself so he could have a chat to the witcher. Through questioning, O'Dimm tells Geralt that he is neither demon nor djinn and that it is not his fault that the negative intentions of his clients cause them to suffer, explaining to Geralt that he gives people exactly what they wished for. When questioned about who he is O'Dimm becomes deadly serious and tells Geralt that those who know his name have either gone mad or have died and he is giving the witcher a small mercy by not telling him. He orders Geralt to bring Olgierd to a meeting at the ruins of an old temple to complete the deal, killing the interrupting drunkard with a spoon on his way out, just before restoring the flow of time.
Geralt can learn from the professor he can challenge O'Dimm to a bet to circumvent the deal as, though deviously clever and merciless, even he can be tempted into pacts and must always keep his end of the bargain. O'Dimm greets both Geralt and Olgierd at the temple ruins by walking down from the sky, telling Olgierd that he is here for his soul as agreed. Olgierd disputes this by stating that O'Dimm can only claim his soul as per the agreement by granting him three wishes through a third party and for him to "be standing upon the moon" which Olgierd thought to be impossible. Still grinning wickedly, O'Dimm reveals that through Geralt he has done the three wishes and, with a gesture, blows away the dust and dirt off the temple grounds to reveal an old tile floor with a design of the moon, thus fulfilling his side of the bargain evidenced by the contract itself bursting into flames. At this point Geralt can do one of two things; 1- Do nothing and let O'Dimm take his due payment, leaving Master Mirror quite satisfied, after which he will cheerily absolve Geralt of the pact and tells Geralt what a pleasure it was to work with him as he offers him an additional reward (which Geralt can decline) before he walks off with the skull of his victim. OR: 2 - Try to help Olgierd by playing for his and Olgierd's souls.If Geralt decides the second option O'Dimm will take him up on that offer on his own terms and promptly sends Geralt to a hellish and twisted landscape filled with shadowy versions of monsters Geralt has fought before. He tells the witcher a riddle which he needs to solve to find O'Dimm and catch him before the time runs out. To add to the challenge O'Dimm also creates illusions and distractions, among them: an illusion of Shani about to fall off a cliff, numerous dead ends and pitfalls, and continuous taunting as Geralt tries his luck. Geralt initially concludes that the answer to the riddle is 'mirror' and eventually manages to find a palace of mirrors, though O'Dimm alters the landscape while causing each mirror he approaches to shatter, all the while mocking Geralt and speaking confidently of his victory. After several attempts, Geralt is able to reason through the problem and comes to the realization that the answer is actually 'reflection', and releases a dammed pool for a water fountain in order to look at himself on the water's surface. As he looks down, he sees O'Dimm hiding in his reflection and pulls him out of the water, which reveals O'Dimm to have eyes like a snake while his cheek and jaw bones become demonic. O'Dimm speaks to the witcher in foreign language before being banished as agreed.
- Geralt has escaped a great many predicaments, sometimes of his own doing, sometimes aided by others. One of the strangest helping hands was that extended to him by Master Mirror. The witcher was on an Ofieri ship, held captive and bound for a date with the gallows... when, out of nowhere, in came Master Mirror. He reminded the witcher of their first encounter, when he helped Geralt find Yennefer in White Orchard. Now he was offering help as well -- this time, for a price. In exchange for freeing Geralt from the ship, he demanded Geralt meet him at a certain crossroads. When the witcher agreed, a strange mark appeared on his face. It was as though Master Mirror had put a stamp on him to show they had entered into as pact – a suspicion later confirmed beyond all doubt...
- Gaunter O’Dimm explained he and their mutual acquaintance, Olgierd von Everec, had entered into a strange pact. Their deal stipulated O’Dimm must grant von Everec three wishes – yet could not do so on his own, but instead had to call upon the services of a proxy. And who better to provide such assistance than a witcher? Since O’Dimm made agreeing to be this proxy a condition for receiving help off the Ofieri ship, Geralt had little choice but to agree.
- Master Mirror appeared once again – suddenly and out of nowhere, as usual – after Olgierd proclaimed his first two wishes. Mirror told Geralt of a way to show Olgierd’s brother the time of his life, even though this life had in fact ended years earlier. He equipped Geralt with von Everec blood and the knowledge of how to summon Vlodimir’s ghost. Just how O’Dimm had managed to collect a vial of von Everec blood was never made clear, but then again, burning question marks hung over everything this strange figure did.
- Master Mirror made an appearance at the wedding Geralt attended with Shani and the ghost of Vlodimir, who inhabited Geralt’s body so that he may enjoy one last night of earthly revelry. When midnight struck, Vlodimir was unsurprisingly in no mood to abandon the pleasures of the witcher’s flesh. Yet Master Mirror intervened to put an immediate and cruel end to Vlod’s stay among the living. Geralt later told me the cries of torment Vlod’s ghost made haunted his dreams for months to come.
- If Geralt seeks out Professor Shakeslock:
- Geralt came away from his meeting with Professor Shakeslock knowing of a way to outfox Master mirror. The demonic pact-maker could be lured into a wager: win it, and he would be defeated once and for all.
- If Geralt chooses to help Olgierd:
- Geralt soon discovered Professor Shakeslock's words were true. Master Mirror could indeed be defeated at his own game. Geralt made a bet with him, wagering everything on one battle of wits, and won. By solving Master Mirror's riddle, he drove the demon from our dimension - though I fear he may yet return. His kind always returns.
Needing the saliva of a spotted wight to brew a potion, Geralt arrives at an abandoned house inhabited by an old lady called Marlene, whom was changed into one as a result of a curse. If the player is able to lift the curse, it is revealed that she refused to give food to a begger, causing him to curse her.
While it was never stated that it was him, the following pieces of information all imply that the begger was in fact Gaunter O'Dimm.
- A letter found inside the abandoned house states that the begger sold mirrors.
- It was mentioned that the beggar broke his spoon before casting the curse, just like O'Dimm did before wrecking the ship that was holding Geralt captive.
- O'Dimm's theme plays in the background while Geralt explains Marlene's curse to his majordomo.
- Randall Flagg - character from novels written by Stephen King has lot of names and one of them is Walter o'Dim. Gaunter also shares similarities with Leland Gaunt from "Needful Things" - an evil entity who grants human wishes in exchange for evil deeds.
- Pact with Olgierd is a reference to Mr Twardowski, a story taken from polish folklore.
- Gaunter O'Dimm is an acronym for G.O.D.
- By stopping time at will, summoning a storm, and stealing souls without showing any sign of effort or focus to do so, one can assume he is the most powerful character ever to appear in The Witcher series, surpassing even Ciri's Elder Blood - though he said that Ciri was "out of his range" and he could not tell Geralt where she is.
- Both times he unfreezes time and consequently disappears out of thin air, a person immediately mentions the word "devil" in a sentence. In both times he also had a wooden spoon.
- Strangely, despite his clear enjoyment of making deals and claiming payments, he does not explicitly ask payment for his first assistance (in White Orchard). This is likely because of how simple the deal was, as there would be no point to ask for payment.
- Only possibly two men from the North ever beat him at his challenge: Geralt of Rivia (if he chose to challenge O'Dimm from taking Olgeird's soul) and an unknown one before him.
- Gaunter's character seems to represent certain aspects of the characters "Holländermichel" and "Glasmännlein" (ger.: glas-man), from the German fairy tale "das kalte Herz" (ger.: the cold heart) by Wilhelm Hauff. In this story the benevolent forest spirit "Glasmännlein" grants the protagonist 3 wishes but, much like in the game, at first only 2 and later the 3'rd. Later in the story the protagonist makes a deal with the evil scorcerer "Holländermicher" who takes his heart and gives him in return a heart of stone and an infinite supply of money.