Up north we enter Petalburg Forest. There is an air of mystique in this place, and I think it can be sensed in the theme alone. Take a listen:
https://m.youtube.com/watch?v=JQb_b5y4hl8I could imagine Junichi Masuda, the director of these games, helped base Petalburg Forest off of real life experiences he had messing around about his summer home in Kyushu as a kid.
There are two more new Pokemon to be found here: Shroomish and Nincada.
Shroomish is vastly usable Pokemon. Firstly, you may have already been the victim of its Effect Spore ability against a Lass on Route 103. Upon contact with Shroomish opposing Pokemon have a 10% to be paralyzed, put to sleep, or poisoned. This is just the tip of the mushroom, however, as Shroomish already has ways to guarantee it annoys you with access to Stun Spore and Leech Seed both by level 10. It gets Mega Drain at 16, and both evolves into grass/fighting type Breloom at level 23 and learns the +1 priority move Mach Punch. It later like Blaziken gets Sky Uppercut at level 36.
While this all may seem moderately good at the first glance, there is one important thing I forgot to mention about our pals Shroomish and Breloom here. You see, if you're crazy enough to do it, Shroomish actually learns one more incredible move after level 23 when it would normally evolve. No, it's not Giga Drain, though it does get that as a TM. At level 54, a level you'd be lucky to be by the time you finished the main story, Shroomish gets access to the incredible move... Spore, a 100% accuracy sleep move. Paired with moves like Leech Seed, Substitute (TM), and Focus Punch (TM), Breloom at a whopping 130 base attack stat is a potentially OVERWHELMING threat to just about any Pokemon that can't OHKO it before it does its magic. This Kangashroom is very deadly if raised right, and can help turn the tide of many battles in the post game alone of Pokemon Emerald!