After completing your mission at Silph Co. and getting all the other 7 gym badges, return to Viridian City and enter the gym. This gym has a maze with items and arrow tiles that make you spin. You’ll battle a few trainers as you navigate the maze. Once you solve the maze, you’ll take on Giovanni once more. Giovanni uses Ground type Pokémon. Dugtrio has great Speed and will use Dig to avoid attacks the first turn then strike the next turn. Nidoqueen will use Body Slam to paralyze targets while Nidoking will use Thrash to repeat for 2-3 turns then become confused. Rhydon knows Horn Drill and Fissure, both of each move that takes an opponent down in one hit but doesn’t work if a target is faster. After winning, you’ll receive the Earth Badge and a TM27 (Fissure). Fissure is a Ground type move that takes an opponent down in one hit but won’t work against faster targets. ... https://www.youtube.com/watch?v=Ou9YEFjPL-8

After triggering a flashback that showed N in the Chargestone Cave via Memory Link feature, his Pokémon will be released and scattered all over Unova. Explore the Chargestone Cave and you just might encounter a Ferroseed that will sparkle, representing that N used to own it. It will be on Level 28. It has a Bashful nature and the ability Iron Barbs, damaging those that make direct contact. Once you capture this Ferroseed that N formerly owned, you cannot give it any nicknames. ... https://www.youtube.com/watch?v=lNJ8wv8uyfM