Brainwashed replicas of Shurelia's personal Guardian, these monsters are relatively tough, although comparatively easier than the ELMA-DS that summons them. The only attack they have is Bugs Fang, which deals average physical damage, and despite their relatively high HP pool, they aren't much of a threat, so you should just use them as stepping stones to raise your Harmonics levels while bidding time for either Aurica or Misha to charge the best songs they can use at the moment. Consider also using the skills of your Vanguards, such as Double Beat or Smoke Bomb in order to dispose of them faster.
This time around, both the ELMA-DS and the ELMAs got a massive boost in stats, aside of gaining new attack skills. Aside of the Bugs Fang, they can also use Shutter Tail and Needle Rain, both of which cause physical damage to a single target, but what makes them more dangerous is the fact that they have access to a Lv. 2 Stored Attack called Break Spin, which can deal large amounts of damage, despite being weaker than the ELMA-DS's Harm Wave attack.
However, their defense got lowered, so they are easier to defeat. However, you should concentrate in just defeating the ELMA-DS, as it can summon more ELMAs, making the battle endless. However, if you want to defeat them in order to lessen the number of attacks your will receive, use the skills of your Vanguards or strong attack items in order to deal damage to all of them at once.
One ELMA is fought in the third episode of Shurelia's Binary Field, but as it was the case with all the other enemies featured in it, its stats were severely decreased in order to allow an easy battle for a party composed of just Lyner and Shurelia. Upon defeating it, Shurelia gains the ELMA-DS Song Magic, which allows her to summon either a ELMA or ELMA-DS (depending on the Burst Lv.) to battle to cause Ice-elemental damage to all enemies.