If you're looking to add a little heat, metal and brain power to your team, you might want to look into grabbing Heatran and Cresselia. These two Legendaries are relatively easy for you to get your hands on, all you need is Surf and an Eon Flute to Soar.
There's really no reason to not try and grab these two Legendaries – they are just too easy for you to grab.
Before you head into battle to capture these two, make sure that you have enough HP restoring items and Poké Balls!
Without further ado, here's how to grab the two:
Heatran
Heatran, the Fire – Steel type Pokémon, can be found prior to completing the main story — you can catch it before the eighth gym leader.
This Pokémon is relatively easy to encounter, all you need to get to it is the ability to Surf (although, Soaring does make travel time faster). Get to Fortree City by Soaring or however you would like and head West to Route 120, use Surf on a small pond under a bridge and head around to a cave. Go inside the cave (optional time to use Flash for better visibility) and head down until you find Flannery.
Flannery will be looking for Heatran, but the truth is, Heatran is all yours. Head down the staircase behind her deeper into the cave system (another optional time to use Flash), in this area you want to head up towards a big opening in the cave floor. Descending into the area will bring you to a room with a ring/portal. Interacting with the ring will bring you to an encounter with a level 50 Heatran.
Cresselia
In Pokémon Omega Ruby and Alpha Sapphire, there are random daily 'Mirage Spots' (the shiny islands you see while Soaring). Cresselia can be found on one of the daily mirage spots on an island called Crescent Isle. Look for it South of Ever Grande City. Landing on the Isle will bring you to a ring/portal, if you interact with it you will meet a level 50 Cresselia.
Here's where you can find guides for catching legendary Pokémon and finding Mega Stones.
