Mind-Seeker

Wrote several trackers (completing 17 of them is sufficient)
Complete guide: https://wowhead.com/news/380212

Mounts:
/run local l={802,36,109,14,64,32,203,154,27,4,37,21,153,157,130,5,374}local p,c=0,0 for _,v in ipairs(l)do p=p+v local n,_,_,_,_,_,_,_,_,_,h=C_MountJournal.GetMountInfoByID(p)if h then c=c+1 else print("Missing: "..n)end end print("Mounts: "..c.."/17")

Pets:
/run local l={2136,216,59,384,93,177,227,971}local p,c=0,0 for _,v in ipairs(l)do p=p+v if C_PetJournal.GetNumCollectedInfo(p)>0 then c=c+1 else print("Missing: "..(C_PetJournal.GetPetInfoBySpeciesID(p)or p))end end print("Pets: "..c.."/8")

There are still a few achievements I'm too lazy to write the tests for. Just search for them yourself.
Achievement: Leaders of Scholomance
Waist Cosmetic: [item=162690]
Toys: [item=190196] [item=201933]
Zuldazar Treasure: [object=296454] (You can check the guide here: [item=163213])

Going clockwise while facing the mural centrally, these are the "secrets" that I can see exist from my character. Click on the items to find relevant info/guides, and thank you WoW Secret Finding Discord for all the fun!

1. 
   
2. Record of the Secrets Behind You - Slime Serpent
3. 
   
4. Record of Drak'Thul's Madness - [item=138201]
5. 
   
6. Record of Taming the Maw - [item=184168]
7. 
   
8. Record of the Riddler - [item=147835]
9. 
   
10. Record of Abyssal Blood - [item=161479]
11. 
    
12. Record of Rising Ashes - [item=193373]
13. 
    
14. Record of the Cavern of Consumption - [item=142223]
15. 
    
16. Record of Collective Courage - [item=184400]
17. 
    
18. Trophy of Revelations - Mind-Seeker itself.
19. 
    
20. Record of Collaborative Cogitation - [item=190196]
21. 
    
22. Record of Ephemeral Crystals - [item=138258]
23. 
    
24. Record of Buried Treasure - [object=296454]
25. 
    
26. Record of a Friend in the Darkness - [item=153195]
27. 
    
28. Record of Cartel Cyphers - [item=186639]
29. 
    
30. Record of Ominously Ordinary Pebbles - [item=162578]
31. 
    
32. Record of Time Waisted - [item=162690]
33. 
    
34. Record of Karazhan's Kitten - [npc=159783]
35. 
    
36. Record of Slippery Find - [item=198870]
37. 
    
38. Record of a Dominant Hand - [item=186713]
39. 
    
40. Record of Mimiron's Master Mind - [item=210022]
41. 
    
42. Record of the Siren's Song - [item=232639]
43. 
    
44. Record of Grggly Stash - [item=169202]
45. 
    
46. Record of a Bad Horse - [item=182614]
47. 
    
48. Record of the Hivemind - [item=156798]
49. 
    
50. Record of the Endless Nightmare - [item=151623]
51. 
    
52. Record of Necromantic Knowledge - Memory of Scholomance
53. 
    
54. Record of Lost Obsidian Treasures - [item=201933]
55. 
    
56. Record of Drust Rituals - [item=163497]
57. 
    
58. Record of Visions of Void - [item=211089]
59. 
    
60. Record of Glimmering Hope - [item=180034]
61. 
    
62. Record of Indecipherable Mo'arg Technology - [item=229348]
63. 
    
64. Record of Rumors - [item=208151]
65. 
    
66. Record of Doug Roberts, Enigmatic Explorer - Hidden behind westernmost pillar, easter egg.
67. 
    
68. Ensemble: Fashion of the Fanatic Felcyclist - [item=246973]
69. 
    

I made a Google spreadsheet tracker if anyone else wants to use it.

https://docs.google.com/spreadsheets/d/1iq0hcp08KvlZfClmRM1Op8fmwYiQBI702Js-UigdsGA/