Walkthrough
At the end of the Canyon Entrance is Sevault Canyon. This large path is home to some of the toughest trainers you will find in the entire game, as well as some of the best Wild Pokemon you will be able to obtain. Within the Sevault Canyon is a HM Strength Puzzle that must be solved in order to open the tombs in the Tanoby Ruins (which is located just south of Sevault Canyon).
Wild Pokemon
Grasses:
Geodude (20%): Level 46
Phanpy (20%): Level 20
Fearow [15%(LeafGreen)/10%(FireRed)]: Level 50
Meowth (10%): Level 43
Cubone (10%): Level 46
Marowak (10%): Level 52
Persian (5%): Levels 49-52
Onix (5%): Level 54
Skarmory(FireRed) (5%): Level 30
Larvitar (5%): Levels 15-20
Geodude (65%): Levels 25-40
Graveler (35%): Levels 30-50
Pokemon Trainers
Cool Couple Lex & Nya: Level 52 Miltank, Level 52 Tauros
Tamer Evan: Level 48 Sandslash, Level 48 Lickitung, Level 49 Ursaring
Pokemon Ranger Jackson: Level 49 Tangela, Level 49 Exeggcute, Level 49 Exeggutor
Pokemon Ranger Katelyn: Level 52 Chansey
Crush Girl Cyndy: Level 48 Primeape, Level 48 Hitmontop, Level 48 Machoke
Cool Trainer Leroy: Level 47 Rhydon, Level 48 Slowbro, Level 47 Kangaskhan, Level 48 Machoke, Level 50 Ursaring
Cool Trainer Michelle: Level 47 Persian, Level 47 Dewgong, Level 48 Ninetales, Level 48 Rapidash, Level 50 Giragarig
Pokemon Trainers - VS Seeker Rematch
Cool Couple Lex & Nya: Level 57 Miltank, Level 57 Tauros
Tamer Evan: Level 52 Sandslash, Level 52 Lickitung, Level 55 Ursaring
Pokemon Ranger Jackson: Level 53 Tangela, Level 54 Exeggutor, Level 55 Exeggutor
Pokemon Ranger Katelyn: Level 56 Chansey
Crush Girl Cyndy: Level 54 Primeape, Level 54 Hitmontop, Level 54 Machamp
Cool Trainer Leroy: Level 52 Rhydon, Level 54 Slowbro, Level 52 Kangaskhan, Level 52 Machamp, Level 55 Ursaring
Cool Trainer Michelle: Level 53 Persian, Level 53 Dewgong, Level 54 Ninetales, Level 54 Rapidash, Level 56 Giragarig