The Impermanence Heron echo is a game-changer for Sub-DPS characters, particularly those utilizing Moonlit Clouds. By equipping this echo, the character's Resonance Energy and the ATK of the next character to take the field are significantly boosted. Furthermore, the skill itself packs a punch, dealing a whopping 300%+ total Havoc DMG. This makes it an ideal choice for any Sub-DPS looking to maximize their damage output.

For supports that scale with HP, the Fallacy of No Return echo is the way to go. It's especially effective when paired with Shorekeeper, currently the best healer in the game. One of the standout features of this echo is its ability to rapidly charge Concerto Energy, allowing resonators to continue acting while Fallacy unleashes a flurry of punches.

When it comes to Sub-DPS characters that rely on coordinated attacks, Hecate is the echo of choice. As long as these coordinated attacks land critical hits, the current resonator's ATK is increased. Additionally, the echo effect summons blades that can attack even when the character is off-field, making it a valuable asset in any team composition.

The Nightmare Inferno Rider echo is a force to be reckoned with on the battlefield. Not only does it deal significant damage, but it also increases the character's ATK for 15 seconds after skill activation. With the ability to deal up to 270% damage and traverse the overworld quickly, this echo is a versatile and powerful tool.

The Nightmare Crownless echo is a high-damage dealer that can be summoned to unleash a total of 270% damage. One of its key features is the ability to charge up the skill up to three times, allowing for multiple uses of the echo skill in a single battle.

For Electro DPS characters, the Nightmare Tempest Mephis echo is one of the top choices. It's essential to determine whether your Resonator scales off Resonance Skill or Resonance Liberation, as this will dictate whether Tempest Mephis is the right fit. This echo also grants access to Empyrean Anthem sonata effects, making it a viable option for coordinated attack Sub-DPS characters.

The Nightmare Thundering Mephis echo is another top contender for Electro DPS characters. Similar to Tempest Mephis, it's crucial to assess whether your Resonator scales off Resonance Skill or Resonance Liberation. If the latter, Thundering Mephis is the way to go, providing a significant boost to your character's damage output.

The Reminiscence Fleurdelys echo is a primary choice for Gusts of Welkin and Windward Pilgrimage 4-cost echo. It provides an Aero DMG Bonus to the wearer, with an additional 10% bonus if worn by Aero Rover. This echo is also a great enabler for Ciaccona and a definitive echo set for the Erosion DPS, Cartethyia. One of its unique features is a small window of time-slowing effect, allowing for uninterrupted damage dealing.

The Lady of the Sea echo is a primary Aero Crown of Valor 4-cost echo. Its echo skill is particularly useful for grouping enemies, making it ideal for taking on mobs. As a summon-type skill, it won't interrupt any combos, ensuring a seamless battle experience.

The Nightmare Lampylumen Myriad echo excels at providing passive Glacio DMG Bonus and Coordinated Attack DMG buffs. While it deals significant Glacio DMG, its usefulness is somewhat limited compared to Hecate, as not all resonators that deal Coordinated Attacks scale off Glacio DMG Bonus.

The Capitaneus echo is the go-to choice for characters that utilize Spectro Frazzle, such as Zani and Phoebe. It's a better option than Nightmare: Mourning Aix, as it provides Heavy Attack DMG unconditionally. However, farming this echo can be challenging due to its 3-cost nature.

The Nightmare Impermanence Heron echo is geared towards Sub-DPS characters in Havoc teams, making it somewhat inflexible. In non-Havoc team situations, the normal variants of this echo may be more useful. The skill itself deals substantial Havoc DMG, making it a valuable asset in the right team composition.

The Sentry Construct echo is the top choice for those running the new Frosty Resolve sonata effect. It deals significant damage and provides echo bonuses without needing to be summoned, making it a low-maintenance yet high-reward echo.

The False Sovereign echo is tailored to Augusta, providing both Electro DMG and Heavy Attack DMG Bonus. As the only 4-cost Echo in Crown of Valor, it's a high-value option. This transform-type Echo requires some time to deal damage, but the stat bonus is automatic once equipped, making it a convenient choice.

The Lioness of Glory echo is a niche option, primarily suited for Lupa. As the only 4-cost echo in Flaming Clawprint, it holds some value. However, its effect is highly dependent on Lupa, making it less desirable for other units. Unless you're building Lupa, it's not worth farming this echo.

The Nightmare Kelpie echo is currently only viable as the second 4-cost for the 44111 echo configuration of Cartethyia. Its buffs are somewhat underwhelming, as it provides both Glacio and Aero DMG Bonuses without a sonata effect that benefits Glacio characters. As a result, its usefulness is limited to specific team compositions.