When Good is recovered, the group resumes their trek to the Mines, sans Ignosi, but with the hag/witch Gagool reluctantly along to act as guide. Foulata also accompanies them, unwilling to be separated from Captain Good. When they enter the hidden treasure room, Foulata- wisely as it turns out- refuses to go in, instead waiting by the stone entrance. When Gagool triggers the secret mechanism attempting to trap the men forever in the room, she rushes to escape under the dropping stone door but is stymied by Foulata, who bravely struggles with the ghastly creature. She is viciously stabbed by Gagool, but manages to delay her so that Gagool ends up getting squashed by the door. Good riddance, say I. Alas, poor Foulata dies there in the dark; Good is extremely broken up by this, Quatermain mentioning that he isn't the same after her death. Certainly we see a much different side of Good here than the rather bumbling figure of fun he was earlier. Despite the tragic ending to their relationship, it has made Good a better, more serious person.
Gagool is super old and wizened, though still spry... powered by her malice, no doubt. She claims to be even older- hundreds of years old- and since no one in the tribe can remember her not being there, they don't question this. It just adds to the level of fear they have for her. Of course, she's not that old, even though she has knowledge of events from that long ago which no one else has. She does, however, mention at one point her grandmother, who seems to have more or less been in the same line of work. What seems more likely than Gagool being a few hundred years old is her being the last in a long line of grifting hags who passed along their knowledge about how to keep the people in line. And with Twala there to enforce her orders, keep them in line she does, mostly through fear and intimidation. Gagool, as mentioned, is small and old; it wouldn't be difficult for any of the men- or many of them, as the case may be- to physically overpower her. But their fear of her purported sorcery and her power to have them executed keeps the other Kukuanas from rebelling against her and Twala.
Even with Twala defeated- killed by Sir Henry in combat- and threatened with death herself, Gagool remains scheming and defiant until the end, plotting the demise of the Englishmen and no doubt also having plans for Ignosi later on. Underestimated by the three men, she's only thwarted by Foulata's interference and a well-placed stone door. Other than Foulata, Gagool is really the only other woman in the novel but she certainly makes her presence felt; the scene where she's dancing about pretending the spirits are guiding her to "traitors" is probably the creepiest in King Solomon's Mines. Although the one with all the old dead kings propped up at the table is a close second. But for all claims of paternalism, H Rider Haggard has produced a canny and wily female villain who gives our heroes a run for their money.
I haven't said much about the actual search for Sir Henry's brother because it's really just a McGuffin, the excuse needed to send Quatermain and the others on a quest for adventure and treasure. The brother actually plays into the story very little, and they locate him accidentally, while on the way home from their excursion to the Mines. He's almost an afterthought, and it seems rather like Haggard is just quickly wrapping up the loose ends of the story so he can conclude it.
So those are my thoughts about King Solomon's Mines... it's a fun story and a rollicking good adventure; I can see why it became so popular at the time of it's release. It's probably a one-time read for me because this really isn't my genre but I enjoyed it for what it was.