Fields of Mistria Ancient Firefly — Where to Catch It
The Ancient Firefly in Fields of Mistria is caught in the Ancient Ruins, floors 81–99 of the Mines — not on your farm, not at the Beach, and not along the Eastern Road. It is a common bug available in every season, any weather, and at all times of day, so once you can enter the Ruins, you can catch one whenever you like. It sells for 40t and is best known as one of the five ingredients of the Dragon-Forged Core.
Where to Catch the Ancient Firefly
Ancient Fireflies are found only in the Ancient Ruins, the fifth and final biome of the Mines. The Ruins span floors 81–99 and unlock through the story quest "Breaking The Ruins Seal" at the bottom of the Lava Caves, so this bug is strictly a late-game catch — if you are still working through the Upper Mines, Tide Caverns, Deep Earth, or Lava Caves, it is simply out of reach for now.
Bugs caught in the Mines have no season or time requirements, and the Ancient Firefly is no exception: the wiki lists it as all-season, any-weather, all-day. That makes it far more flexible than its overworld cousin, the regular Firefly, which only appears on summer nights and sells for a mere 10t. Because the Ancient Firefly is common rarity, you should not need many floor resets to spot one. Keep in mind that leaving an area and coming back resets which bugs are currently present, so hopping between floors is a valid way to reroll spawns if a floor comes up empty.
The Ruins are dark — each floor is shrouded in darkness until you light it with Mistril equipment or the Sacred Light spell — and they are patrolled by monsters, so bring combat gear even for a "quick bug run". While you are there, the same floors also hide the Giant Worm (uncommon, found when breaking rocks), the Hidden Beetle (rare, 90t), the Parchment Moth (uncommon, 80t), and the Void Snail (common, 40t), which makes a catching trip easy to combine with museum hunting and Voidite mining.
How to Catch Bugs in Mistria
Catching any bug requires a bug net and at least one energy — though the swing does not actually consume energy. You get the Worn Bug Net from Luc: a few days after you settle in, he sends mail that starts the quest "Something's Bugging Me", and you then meet him at the inn in town to receive the net.
The Worn Bug Net is genuinely all you need. The fancier nets crafted through blacksmithing are not any better — they only have a different appearance — so do not spend ingots on an "upgrade" for catching purposes. Equip the net, walk up to the firefly, and press the interact key to swing. Some bugs are quick, but they do not run away if you miss the first swing, which makes the slow-drifting Ancient Firefly an easy target.
Bug catching is one of the easiest side incomes in Mistria: you simply run around the map swinging the net, and it combines naturally with farming and foraging to fill your backpack with sellable loot. Elsewhere in the Mines, some bugs only appear when you cut grass, chop trees, or break rocks — but the Ancient Firefly is a straightforward visible spawn, so no extra tool work is needed beyond the net.
What the Ancient Firefly Is Used For
The Ancient Firefly has four main uses:
- Museum donation — it can be donated to the Museum's Insect Wing, where it belongs to the Ruins set. Reina's museum comment says the firefly on display is "so pretty, like a fairy," which matches its in-game description of an almost fairy-like appearance.
- Terrarium — placed in a Terrarium alongside 4 other common insects, Ancient Fireflies produce Common Fish Bait and/or Common Bug Pheromones once every 3 days, after the Terrarium's request has been completed.
- Dragon-forging — it is one of the five ingredients of the Dragon-Forged Core (Monster Core ×5, Mistril Ingot ×1, Pink Diamond ×1, Ancient Firefly ×1, Medium Essence Stone ×1), which is required for the "Repair the Bell Tower" story quest. See our Dragon Forged Core guide for the full recipe.
- Selling — at 40t each it is modest but effortless income while you are already in the Ruins for other reasons.
The Dragon-Forged Core recipe only needs one Ancient Firefly, so a single catch covers the Bell Tower quest — but donating one to the Museum first is a good habit so you never have to climb back down just for the Insect Wing. A simple catch plan: one for the Museum, one for the Dragon Forge, and any extras into a Terrarium or the shipping bin.
Like the other Ruins materials, the Ancient Firefly was added in the v0.15.0 update, so guides written for earlier versions of the game will not mention it at all.
Gifting: Who Actually Wants One
Think twice before handing this bug to your neighbors. Ancient Fireflies are universally disliked as gifts, with only four exceptions who feel neutral about them: Dell, Dozy, Henrietta, and Luc.
Everyone else — including all twelve marriage candidates — dislikes receiving one, so gifting an Ancient Firefly costs you friendship instead of earning it. If you are working on a romance route, check our romance guides and bring something the recipient actually likes; save the fireflies for the Terrarium, the Museum, and the Dragon Forge. And if you simply must gift a bug to someone, Luc is at least a thematically fitting choice — he is the villager who mails you your first net.