Head to Urialla Harbor on An Skellig to find it's raining nonstop. As soon as you arrive, you'll also overhear several men in the center of town talking about a tower causing the bad weather and, once you get close enough, they'll spot you and call you over.
Talk to them and one will lead you off, explaining how the tower appeared out of nowhere and with it, the nonstop rain. Several of their men went inside with a druid to investigate but haven't been seen since.
Head out and enter the tower to find right down the stairs what the man had been talking about earlier: a portal. Head through it and you'll come out into another part of the presumed tower, but the portal you used immediately disappears as you hear and see a golem in the central part of the chamber while a voice announces an intruder, that is to say, you. The golem will then home in on you so naturally you'll need to kill it off before investigating further.
Once dead, a man behind the barrier to the left when you entered will call to you, but you can examine the body in the middle of the room or near the man's archway first to find what happened to the earlier party. Now go and talk to the mage, who reveals himself as Sigo Buntz, and that the tower is outfitted with a Defensive Regulatory Magicon (DRM) so only the (now deceased) owner could use it. Before the new owner could disable it, it'd sealed off the rooms, summoned the golem, and, unknown to Sigo, teleported the tower from Kovir to Skellige. Turns out a side effect of the teleportation was the rain, so you'll need to find a way to get the tower back home. Sigo will then inform you that you must find the previous owner's Gottfried's Omni-opening Grimoire, which will help Sigo disable the DRM. You can talk with him to learn more about him, the tower, and the earlier party and, once done, he'll use a spell to open the portal across from him so you can try to find the grimoire.
Enter the new area which is flooded, and swim until you find two submerged archways, then go to the room on the left. Just as you get onto solid ground, DRM activates and will start to summon monsters after each one is killed as follows: 3 alghouls, a gargoyle, a werewolf, and finally, a non-violent cow. Once the hostile creatures are dead, you can now safely loot the key to library from the chest on the table. You can also examine the remains of another one of the missing Skelligers in the center area, where the monsters were being summoned.
With key in hand, head back out and this time go to the other archway to unlock the library's door. Before you start examining the books here, it's best to loot anything and examine the body here as, when you find the right book, the DRM will kick in again. When ready, examine the books to find GOG and the room will start to fill with gas. Thankfully it's only limited to that room so just go back out to the flooded passageway.
Go back to Sigo and he'll be able to remove the barrier to the room he was in before stating the hardest part was to come: the tower will throw everything at you in the final area while Sigo tries to disable the DRM. You can tell him you need time to prepare or go for it here. In the final room you'll face an earth elemental in addition to occasional electrical shocks from the room's floor. While these shocks are meant to harm you, if positioned right you can also use them to harm the elemental. Once it's dead, talk to Sigo who'll thank you and give you Moonblade before teleporting the tower back to Kovir, but not before teleporting you back to Urialla Harbor, right into the ocean.
Swim back to the village and, once close enough, the villagers will thank you and offer you a reward. You can accept it for an additional 65 or inform them Sigo already paid you. Regardless they'll thank you and walk off save for one: he'll ask if you saw his brother while in the tower. You can tell him the truth, in which case he'll be sad at the news, or lie and he'll hope that his brother survived somehow. Regardless, the quest will then complete for 50 .
- Wind-whipped and rain-battered, Geralt stumbled into a small village on the coast of An Skellig. The foul weather, he learned, had cursed this spot ever since a mysterious tower appeared one morning out of thin air, as if placed by an invisible giant's hand. Intrigued, Geralt decided to investigate.
- While traversing the An Skellig coast, Geralt suddenly found himself beset by a fierce storm. A tower stuck awkwardly out of a nearby hill, and, though his medallion tingled as he neared it, Geralt decided to seek shelter there from the driving rain...
- The tower, as one might have predicted, was endowed with magic. To be precise, it was equipped with a Defensive Regulatory Magicon, a mystical apparatus that treated every entrant save the tower's original owner as a dangerous intruder. That is why it had locked Sigo Buntz, the Koviri mage who had purchased the tower at auction, in a cell inside his new property. It tried to do the same with Geralt, but to a determined witcher, a tower full of magic trickery is no obstacle.
- Following Sigo's instructions, Geralt found a tome in the depths of the library entitled "Gottfried's Omni-opening Grimoire." He and the mage used the secrets contained within to disable the tower's defenses. Once free, Sigo, bursting with gratitude, rewarded Geralt (generously, I hope, for the witcher never said exactly how), transported him in a flash to the village where it had all started (well, to be precise, to the bay off the coast from the village), then whisked the tower away for good. Once it was gone, all that remained of the storm were a few puddles and scattered clouds in the otherwise bright and sunny sky. The gathered villagers went wild with joy and showered Geralt with well-deserved thanks.
- Talk to the villagers.
- Enter the tower.
- Explore the tower.
- Defeat the golem.
- Talk to the man trapped behind the magic barrier.
- Find the key to the library using your Witcher Senses.
- Enter the library.
- Find "Gottfried's Omni-opening Grimoire" using your Witcher Senses.
- Bring the mage "Gottfried's Omni-opening Grimoire."
- Break the tower's defenses with the mage's help.
- Talk to the mage.
- Talk to the villagers.
- This quest is the developer's jab at the practice of digital rights management (DRM). While the tower was purchased pre-owned by the mage, making him the legal owner of it, he's not the tower's original owner, and thus the tower's Defensive Regulatory Magicon (DRM) locks him out of his own tower. The book (GOG) is needed to unlock the tower and is a reference to GOG.com which is a service that provides access to DRM-free games, and a wholly owned subsidiary of CD Projekt.
- There are several invisible NPCs in various places in the tower. While they are invisible, the player can notice their presence accidentally by bumping into them, causing them to emit the sounds that regular NPCs make when Geralt bumps into one. Geralt's "bumping into people" animation will also denote their presence. Players have speculated that these NPCs may be a workaround to allow the game to play back the voiced warnings that the tower's defense system gives while there's no visible NPC to say the lines.