Fire Emblem Echoes: Shadows of Valentia is the next entry in the Fire Emblem franchise, but it's far from the standard strategy-RPG framework you've come to expect from the series. That's due to its heritage, as a remake of Fire Emblem Gaiden for the Famicom. That game itself was a spin-off from the main franchise, which allowed it to experiment and take risks outside the traditional Fire Emblem tropes. Bringing back those experimental elements, along with some dashes of modernizing, makes for a unique hybrid of old- and new-school design.
Exploring Dungeons and Towns
The most clear and obvious change from the standard Fire Emblem formula is the addition of dungeons that can be fully explored in 3D. At least, to a point. These are relatively small and contain only a few enemies. and treasure stashed in destructable crates and barrels. It's not the most elegant part of the design, as controlling the character and camera can feel clunky, but it is very different.
To a lesser extent, you can also explore Towns. These aren't fully rendered in 3D, and are instead modeled as static images. You can talk to townsfolk, which you absolutely should do as sometimes that will allow you to recruit them, and look around for bits of food or weapons lying around. Imagine the room scanning elements of Phoenix Wright and you have the right idea.
Another mainstay of more traditional Japanese RPGs, Echoes brings in a kind of random battle system. When roaming dungeons you will see enemies wondering about. They can be avoided entirely, or you can run into them or strike them with a weapon to start a battle. This takes you into a second screen where you engage in a traditional Fire Emblem battle against multiple enemies. These skirmishes are a little easier than the story battles, but can still go on for a length of time, which is why dungeons are generally so sparsely populated with them. Make sure to hit the enemies whenever possible in the dungeon exploration areas, as that will shave off a little life from all of them in the strategy segment.
Recent Fire Emblems have made upgrading classes a pretty straight-forward process. You get some supply of Master Seals throughout the game, and you can use them to upgrade any character who has reached level 10. In Echoes, though, your upgrades are tied to the dungeons. Near the end of each dungeon you'll find a statue of a goddess. By approaching it you can upgrade any character who has gained sufficient levels, as well as give an offering for special effects like restoring status ailments. Usually, in a small room beyond the goddess, there will be a spring that gives you three stat upgrade points to spend on your characters.
Magic in Fire Emblem Heroes is stronger than most other Fire Emblem games, and as a trade-off, using it actually hurts you. Casting a spell will cost you some (usually small) amount of HP, which both mitigates the strong effect and makes for strategic trade-offs. You'll still have to keep magic users near the back line, but this time it's because using their powers will make them more vulnerable to attack. Keeping a healer around doubles as mana restoration to provide fuel for additional spells.
Fire Emblem is notoriously difficult, especially on the Classic setting with permanent death. Echoes allows you to select Casual if you want to avoid permanent death, but it makes Classic more appealing with the addition of a new item. Part of what makes Classic permadeath so galling is the need to start from scratch. It's frustrating being nearly done with a battle only to have a stray arrow kill one of your MVPs and then be left with the choice of restarting the battle entirely or letting them die. A new time-turner lets you rewind a battle to an earlier turn with a great degree of precision. You can only use it so many times in a single battle, but it's the perfect solution for those occasional annoying deaths that you couldn't really see coming.