Children of Zodiarcs

This achievement IS missable if you do not do the skirmishes with Nahmi and company.

You can tell the difference between skirmishes and elite skirmishes by their logo on the map; skirmishes are red and black, elite are red and white. Skirmishes are your usual "kill everyone" missions, they're there for grinding levels and dice. But the elite are much more difficult than their normal counterparts. Sometimes it's enemies with serious HP boosts, sometimes it's dice roll RNG buffs, sometimes it's just a massive wave of enemies that is hard to manage, and sometimes it's a hodgepodge of all three. They appear randomly in mission spots you've previously cleared, and regarding strategy, you're going to have to bob and weave your way through the battlefield and pick off everyone one at a time. Take advantage of spread AoE moves, and don't be afraid to use your healing liberally since you'll (almost) always have two very competent healers on your side.