Revealing mistake: When Dracula walks up the wall (the first time we see him in color), in the overhead shot the torches wobble slightly from where the separate photography was composited in. (00:34:25)
Continuity mistake: When Anna is looking for her brother who fell off the cliff, there is a closeup of her where you can see some bushes in front of her. When it cuts to a wide shot you can see there are no bushes anywhere near where she is standing. (00:22:10)
Factual error: In the beginning of the scene after Van Helsing kills off one of the three female vampires, there is a map behind Friar Carl depicting the whole of the Carpathian basin, which, at the time, included the Austro-Hungarian empire as well as a part of Romania. However, the whole area is labeled "Transylvania", which is only a region of Romania.
Continuity mistake: When the werewolf is down the trap you see Anna placing her foot on the edge of the hole. As the cage is being dragged up you see Anna do a backflip. However in one of the scenes you see her backflip you can see her actually standing two feet away from the edge before she does the backflip. (00:20:55)
Continuity mistake: When Carl explains everything about vampires and Van Helsing wonders how he knows so much about them, Carl says "I read". Then he notices the 'Glycerin 48' and says "Ah." The shot changes, and now Carl suddenly has his hand up. (00:17:55)
Revealing mistake: At the ball when Carl pushes the man spitting fire so that he spits fire on Dracula, you can see Dracula grabbing him and throwing him away. Then it cuts to Van Helsing gliding down on a rope grabbing Anna. When we get to the scene where the camera view comes flying against Anna we can see, on the left, Dracula's shadow when he is throwing the man. As the previous scene where Dracula threw away the man was most likely done with CGI, they forgot to add the man's shadow in this scene. Also in the following scene you can see Dracula throwing, but this time they forgot to add the man in. (01:23:35)
Revealing mistake: When Velkan and the werewolf has dived off the cliff, we get a shot behind Anna where she is looking down the cliff. It cuts to a front shot of her and back behind her again and you can see it's actually the same scene played over again. You can easily see it on how her hair moves in the wind. (00:22:00)
Continuity mistake: When Carl picks up the silver stake Van Helsing is holding the bag with clenched fists. When it cuts to Carl putting the stake into the bag, Van Helsing is holding both his thumbs up. (00:17:30)
Revealing mistake: When Dracula pulls the silver stake from his heart, you can see it is a prop from the way the point wobbles slightly. (00:59:35)
Continuity mistake: When one of the brides push Anna and Van Helsing to the ground under the first attack, Van Helsing drops his spike weapon to the ground. The position of the weapon changes during the shots. (00:25:10)
Revealing mistake: At the windmill when the fire reaches the cases with Absinthe bottles the cases explode. Howeverm when the explosion occurs we can see sparks. I'm pretty sure an explosion like this wouldn't produce sparks, so it's obvious the explosion was ignited by some explosives. (00:05:35)
Factual error: After falling from the bridge, the wagon descends into the canyon for 35 seconds before hitting the bottom. This equates to approximately 9,500 feet (1.8 miles) of falling. There is no canyon anywhere near that deep in Eastern Europe.
Continuity mistake: Before Van Helsing looks at Dracula's children in the "eggs" by biting it off and dropping it to the ground, he removes one of his gloves. However, when he starts shooting the offspring, then fighting Dracula, that glove is back on his hand.
Continuity mistake: When Mr.Hyde is charging Van Helsing while saying "Here I come, ready or not", you see Van Helsing standing in front of him holding his blades down. When it cuts Van Helsing is suddenly holding them in front of him. (00:10:30)
Revealing mistake: When the undertaker is about to hit Van Helsing with the shovel, we can see the shovel stop in the air before Van Helsing grabs it. (00:44:50)
Continuity mistake: When the friar is about to stake Van Helsing at the end, it shows him taking an overhand swing with the stake up ready to plunge. Then it cuts and the friar is grasping the stake, which is down by his waist. Then it cuts to the first shot again. (01:52:35)
Revealing mistake: When they are on the border of Danube in Budapest, and the Bride is inviting them to a ball, look across the river at the large building with a golden dome. It's the National Theatre situated in Prague, Czech Republic, where the scene was shot.
Continuity mistake: When Anna is running away from the Wolf Man she is wearing felt shoes but when Velkan pushes her out of the way she is back wearing her high heeled boots.
Continuity mistake: Near the end of the attack of the Brides, Marishka is about to make her final "charge". The wind blows the hair back from her face, showing that she is not wearing any earrings. Yet after Van Helsing kills her and she starts to disintegrate, she is wearing large triangular dangling earrings. (It's not because her jewelry disappears in her flying form - she is shown wearing bracelets and rings in *both* forms).
Continuity mistake: In the scene in the village, after the brides have attacked, Anna lands on top of Van Helsing. In one shot she is sitting with her legs under his arms, in the next shot she sits above his arms. When they roll, her legs are back under his arms.
Answer: After being killed - "murdered" as Dracula stated several times - by Van Helsing, Dracula made a deal with the Devil to regain his life. Carl tells his story when telling Van Helsing and Anna everything that he has learnt.