With over 400 Pokémon to find in Mystery Dungeon: Rescue Team DX, you might expect that not all of them will be as straightforward as the standard way to recruit a Pokémon to your team. SomePokémon can only be caught at certain times, or if you have certain items on you at the time. These are normally high-value Pokémon that you want to find room for in your camps.
Mew is one such Pokémon, and there are a few things you must do before you can recruit them. First, you will need to have beaten Kyorge in the Stormy Sea. A few days later, you will receive a letter that lets you know about the existence of the Buried Relic, a place where Mythical Pokémon can often be found.
You will then need to talk to both Lombre and Shifty, and both can be found in Pokémon Square. After you speak to them, the Buried Relic dungeon will become available. After that comes a trio of fights you will need to win the Buried Relic dungeon:
- Regirock – 15F
- Regice – 25F
- Registeel – 35F
Defeating all three will get you the Music Box. Now that you have the music box, you can begin the search for Mew, who will spawn on a random level between B36F and B99F. After that, the usual rules apply. You will want to deliver the final blow with your Rescue Team Leader, and even then, there will be a small percentage chance that Mew will join you.
Keep in mind, you also need a camp for Mew, and will need to have purchased Final Island Camp to have any chance to recruit this Pokémon.