The Sentry is a quest in Chapter II which begins when, at Kalkstein's request, Geralt asks Vaska about the Mage's tower. She tells him what she knows and gives him the Tower tarot card, saying that she has no more need of it. This tarot card reveals how to defeat the golem which holds one of the keys to the tower.
Walkthrough
After undertaking the Mysterious Tower quest, Geralt runs into some snags. Namely, he needs ten sephirot to open the tower and he can only find eight. It seems that the ninth sephira is inside a currently motionless stone golem in the Golem burial ground in the swamp. Using the tarot card that Vaska has given him and some help from Kalkstein, it becomes clear that the witcher must first wake the golem and then defeat it, in order to retrieve the sephira.
Waking the golem requires a bit of legwork, and it is not cheap either. Firstly, Geralt must have a lightning rod fashioned by either Malcolm Stein (who charges 50 
), or by the Order armourer (who needs instructions and charges 70 ). The choice of blacksmith will depend on which side the witcher supported in Force Recon. Then, once the rod is secured, there comes the question of summoning a storm on demand. Perhaps the druids can help? Yes they can, but it costs another 500 more.
You don't have to pay the 500 orens. There is a much more simple and cheap method. It's also very easy. You can awake the golem without the druids by stabbing it with the lightning rod while it's raining. It doesn't matter if it's sprinkling the tiniest bit. Rain = Free.
Once all the preparatory steps have been completed, there remains the fight with the Sentry, so our hero heads out to the Golem cemetery in the swamp. He finds the beast and jams the lightning rod into it. Since the druid has already summoned the storm, it does not take long for lightning to strike and wake the behemoth. It seems he is less than pleased at being roused.
Next comes a lot of running around. Geralt must touch each of the three stone posts for each "round" of the battle. The first two posts do not seem to do much except attract lightning to themselves. It is only touching the third post that can be tricky. Geralt must be outside the triangular area framed by the posts when he touches the third one, otherwise he will be struck too. The flip side of this is that the golem must be inside that same area or he is not struck.
It takes three successful strikes to kill the golem. At that point, it can be "skinned" and the Neh'tza sephira, plus its obsidian heart can be harvested. Voilà!
Notes
the activation sequence for the posts
- If any of the quests are finicky, this is one of them. Save your game before starting. It is not difficult to kill the golem, it can just be hard to remain standing while doing it.
- Be very careful when activating the stone posts to electrocute the golem. You must be definitively outside and the golem must be definitively inside the triangle they form or you will also be struck by lightning and depending on your level, that might kill you instantly.
- Be warned, the 'triangle' is very iffy, and you might get struck while outside and the golem inside. Be sure you can survive one strike before attempting any lightning strikes, otherwise, you will have a 50/50 chance that the golem will be hit, or you will be hit and die.
- Also be careful of the order in which you touch the pylons, you can start anywhere but must go clockwise or may get struck by lightning yourself.
- Using a potion of Blizzard before you awaken the golem makes this fight a breeze. You will easily be able to get around the triangle without the golem ever coming close to you and you can wait at the third pylon until he is in the triangle. Igni will push him back so if he is hanging around the edges use this to get a guaranteed lightning strike.
- Having a weapon drawn causes you to be struck by lightning. During Force Recon you can use this fact to destroy Scoia'tael and Order forces with the Pylons as they will have their weapons drawn.
- The golem does not move that quickly, so if you have managed to be struck by lightning and survived, just keep running around until your vitality is back up to 100% before continuing. The golem will not "heal".
- You can choose to fight the golem using more conventional methods, you are not forced to use the magic posts, but it is a more difficult (but not impossible) battle.
- You can also get some assistance if the Force Recon quest has been triggered but you have not accepted it yet. The Order's camp is practically right next to the Golem Burial Ground. All you need to do is to lure the golem over to the camp, and they will be happy to help. Note that any Order that die accidentally will probably drop Orens or gear as loot. Nice little bonus on top of the free help. (In all likelihood, if you let the Golem fight the camp, none of them will actually survive.)
- Another way to do this is to lure the golem over to the Scoia'tael camp, and abuse the small walk way bridge leading to the camp. The golem is too large to get on the bridge, and it will just stand there while you shoot it full of Igni fireballs.
- The lightning become permanently active after this quest (even when there is no storm), so if you ever run into trouble in the swamp, you can lure whatever you are fighting to the triangle and zap! Problem solved.
- It is not actually necessary to touch the posts starting with the one labelled 1 (True! but we had to start somewhere). Just run around them clockwise and touch them in order. It does not matter which you start with.
- Wait for a storm. Do a couple other quests, storms are pretty frequent in the swamp, or meditate at the nearby campfire for a couple hours at a time. Instead of meditating for days at stretch in game make a save and load it back again(quick load is pretty useful), there is a good chance that it might rain when you load the game(once in 4 loads approx.).There is no reason to pay the druids except impatience. (One can always just leave the map and come back)
- I think I got it! I removed all the equipment. No metal, no lightning!
- Actually it's really simple in the Enhanced Edition. Just lure the golem into the triangle, activate posts in the clockwise order, and repeat until he's dead.
Phases
A Tarot Card
Vaska revealed to me the story of the tower. To open it, I must consult the Tarot card that illustrates how to defeat the golem that is the tower's Sentry. I need to discuss this with Kalkstein.
The Lightning Rod
To wake the golem up, I have to arrange a lightning storm and get a lightning rod. Piece of cake. First I should find a craftsman — storm without the lightning rod is of little use to me anyway. I must find a craftsman who will make a lightning rod for me.
Money for the Dwarf / Armorer
The Storm
))Druids
Druids can control the forces of nature, so maybe they can summon a storm for me. I don't think they'll do it for free, though. I'll ask the druids to summon a storm.
Money for the Druids
The druids can create a storm for me, but they want 500 orens for that. I have to bring them the money or wait for the natural storm. I must pay the druids 500 orens for the storm.
- Tip: This part and the next can be avoided by simply inserting the metal rod while it is raining, even just slightly, and the normal cutscene will play, saving you 500
.
The Golem
I paid the druids. I hope the storm is worth its price. I must now find the golem, place the lightning rod in its hand and wait for the lightning. I must put the lightning rod in the golem's hand. (–500 )
Waking the Golem
The golem has awoken. I have to defeat it to enter the tower and find the Sephirah. I must defeat the golem.
The Sephirah
I defeated the golem. I must take the Sephirah out. I must remove the Sephirah from the golem. (2000 XP)
The Sephirah
I got another Sephirah, hidden inside the golem. It was not an easy task. I defeated the sentry.
