Torch is an example of a darknet search engine. How can search engine optimization (SEO) be done to make an .onion site appear at the top of search results? how is darknet SEO different than regular Google SEO, where either the number of clicks or paid marketing can move a site to the top?
It is totally up to "designer" of this Search Engine, is not?
Google has published their index-method, it is called PageRank, so here you could at least guess a little bit... Nevertheless, nobody knows all of "The Kitchen" and war for the first places in Google's Search Results is endless...
You could try to tap your target, using kind of reverse engineering hooks.
Lets call your target - Torch.
Lets call the main one - "Directory" and lets place on it - links to 1,000 ( one thousand ) other onions-sites.
Backward, on all of this 1,000 new onions-sites, you should place links to this "Directory", to increase the PageRank of your main-site, called "Directory".
Also, you should place links to "Directory" on all possible places, like reddits, other onions-dirs( for example, https://ahmia.fi/ ), all hidden forums ( like silk road was ), etc...
Now you are ready.
I dont know how long, but you need to wait for day, or may be week, may be month, unlikely year.... Before web-crawler of Torch will index all your 1,000 sites and will increase PageRank of your main-site, called "Directory".
After awhile, you will check your "Directory" in Torch results, and it shall take some top-place. However, Torch might black-list your site, because - it is not real, it is fake / dirty-cloaking shit..
And so on. It is Fighting of projectile and armor.
You will generate new cloak each week/month/year. Guessing how they indexing.... How they far from original Google's PageRank idea...
They will finding you, blacklisting you, and changing all their indexing-algorithms.