After you have obtained the National Dex and fought your way to the Survival Area, you will discover that your rival is there, hanging out in front of the Top Trainer Café. Like in Diamond & Pearl, he will be willing to have a battle against you, but only on the weekend. His Pokémon start up at the same levels as the people in the café. However, they will get higher in stages until they reach a maximum of Level 85 for his starter. This is done after beating the Elite Four 10 times

Rival Battle - Phase 1

Rival If you picked Piplup	Staraptor Lv. 61	Rapidash Lv. 59	Floatzel Lv. 59	Snorlax Lv. 63	Heracross Lv. 62	Torterra Lv. 65
Rival If you picked Turtwig	Staraptor Lv. 61	Roserade Lv. 59	Floatzel Lv. 59	Snorlax Lv. 63	Heracross Lv. 62	Infernape Lv. 65
Rival If you picked Chimchar	Staraptor Lv. 61	Roserade Lv. 59	Rapidash Lv. 59	Snorlax Lv. 63	Heracross Lv. 62	Empoleon Lv. 65

Rival Battle - Phase 2

Rival If you picked Piplup	Staraptor Lv. 71	Rapidash Lv. 69	Floatzel Lv. 69	Snorlax Lv. 73	Heracross Lv. 72	Torterra Lv. 75
Rival If you picked Turtwig	Staraptor Lv. 71	Roserade Lv. 69	Floatzel Lv. 69	Snorlax Lv. 73	Heracross Lv. 72	Infernape Lv. 75
Rival If you picked Chimchar	Staraptor Lv. 71	Roserade Lv. 69	Rapidash Lv. 69	Snorlax Lv. 73	Heracross Lv. 72	Empoleon Lv. 75

Rival Battle - Phase 3

Rival If you picked Piplup	Staraptor Lv. 81	Rapidash Lv. 79	Floatzel Lv. 79	Snorlax Lv. 83	Heracross Lv. 82	Torterra Lv. 85
Rival If you picked Turtwig	Staraptor Lv. 81	Roserade Lv. 79	Floatzel Lv. 79	Snorlax Lv. 83	Heracross Lv. 82	Infernape Lv. 85
Rival If you picked Chimchar	Staraptor Lv. 81	Roserade Lv. 79	Rapidash Lv. 79	Snorlax Lv. 83	Heracross Lv. 82	Empoleon Lv. 85