S-TIER | BUILD MERCENAIRE FLAMEBLAST GEMLING (@josiahyeet) | SAISON 5

Build Video

Build Overview

Josiah (@josiahyeet) revisited his « Floor is Lava » Gemling for patch 0.5.5, and the demonstration is hard to argue with: a character capped at level 60, level 15-16 gems, four-link setups, zero uniques, zero jewels, gear pieces bought for one exalted apiece — and T15 maps cleared without breaking a sweat. The simulation runs live in the video, with 55 passive points still unspent and rares dropping in under a second. This mercenary Flameblast Gemling build costs about twenty exalted to build from scratch.

The setup boils down to two skills. Flameblast charges once, at the start of a map, and drops a massive ignite. Oil Grenade then spreads an oiled ground that carries this ignite and keeps relaying it indefinitely. Flameblast‘s cooldown and its ten-stack charge system — the two real pain points of this skill — both vanish at once: you walk forward, throw grenades, the ground ignites, and everything dies behind you.

Gemling Legionnaire isn’t a cosmetic choice. Gem quality is the main multiplier for ignite magnitude here, and no other ascendancy comes close to these values. That’s also what shapes the progression: each investment tier chases extra quality instead of raw damage. The curve climbs from a twenty-exalted starter version all the way to an endgame build with over 300,000 effective health points, capable of soloing Grand’s Spiritbox farming.

Strengths / Weaknesses

Skill Gem Setup by Step

This build offers 3 progression steps from leveling to the final build. Select a step to see the corresponding gem setup.

level 60 starter 6D budget 225% Rarity Pre MB/HH CoD Zoom

level 60 starter

7 skills • 19 gemmes

Virtuous BarrierVirtuous Barrier

Orbe solaireSolar Orb

Armure arctiqueArctic Armour

BlasphèmeBlasphemy

Grenade à huileOil Grenade

TornadeTornado

ConflagrationFlameblast

6D budget 225% Rarity

8 skills • 30 gemmes

Virtuous BarrierVirtuous Barrier

Orbe solaireSolar Orb

Déclenchement lors d'Altérations élémentairesCast on Elemental Ailment

TornadeTornado

ConflagrationFlameblast

Grenade à huileOil Grenade

Reliquats de ManaMana Remnants

Armure arctiqueArctic Armour

Pre MB/HH CoD Zoom

11 skills • 46 gemmes

Virtuous BarrierVirtuous Barrier

Nova foudroyanteEnervating Nova

Cri infernalInfernal Cry

Cri sismiqueSeismic Cry

TornadeTornado

ConflagrationFlameblast

BlasphèmeBlasphemy

Armure arctiqueArctic Armour

Totem sismiqueShockwave Totem

Grenade à huileOil Grenade

Déclenchement lors de l'EsquiveCast on Dodge

Recommended Equipment

The shopping list is short, and that’s the whole point of this build: aside from the staff, no piece needs to stand out.

• Staff: the only purchase that matters. Look for +5 or +6 to Fire Spell Skills, complemented by spell damage and extra damage as fire. A Desert Rune in the socket, or a +1 rune if the budget allows.
• Amulet: +2 to all Spell Skills, or +1 if the price takes off. The rest into life and resistances. If you land some spirit on it, Cast on Dodge becomes playable earlier.
• Body armour, gloves, boots, helmet: life, armour, resistances, nothing else. Movement speed on the boots.
• Armour base: with Iron Reflexes, evasion converts into armour. So grab the cheapest base on the market — armour/evasion in general, but a pure evasion or pure armour base works just as well.
• ⛔ Avoid at all costs: any added fire damage to attacks on the weapon, gloves and rings. See the dedicated section below — it’s the only mistake that truly breaks the build.
• Higher tiers: Morior Invictus and Ingenuity on the six-divine version, then Loreweave, Darkness Enthroned, Paragon and From Nothing on the zoom version, with the Rite of Passage charm. Mageblood and Headhunter only come after that, and the build runs perfectly fine without them.

Gameplay Tips

• A single Flameblast per map: charge it on entry, let it lay down your reference ignite, and never touch it again.
• Continuous Oil Grenade: this is the skill that keeps your fingers busy 95% of the map. The oiled ground carries the ignite, so all you need to do is lay it down in front of you.
• Tornado by hand for flying monsters. Expeditions are full of them; in regular mapping, Josiah says he almost never has to cast it.
• Arctic Armour in alternate quality: this is what makes T15s survivable. Roughly 300% extra armour, stacked with the conversion from Iron Reflexes.
• Cast on Elemental Ailment on Tornado: convenient, but it triggers stray ignites that overwrite your own. Test it, and switch back to manual casting if your damage tanks.
• Keep moving. Standing still stacks up burning zones and tanks your framerate, without adding any damage.

Burning Ground: The Engine of This Mercenary Flameblast Gemling Build

Flameblast has a design flaw everyone has run into: a cooldown and ten stacks to build up before the skill does anything at all. Playing it on repeat is tedious, which is exactly why you rarely see it used.

The trick here is to cast it just once. The ignite it applies is massive, and Oil Grenade transfers it onto the oiled ground, which holds onto it and spreads it to anything that walks over it. The stack mechanic becomes irrelevant: you pay its cost once, on entering the map, and reap the benefit for the entire duration of the farm.

The effect on the playstyle is clear-cut. You stop aiming at anything, stop following a rotation: you run, you drop grenades, and the damage spreads on its own behind you. It’s a low mental-load build, which matters when you’re chaining maps for hours on end.

The Added Fire Damage Trap

Here is the one real mistake capable of sinking the build, and it goes completely unnoticed if you don’t know about it: no added fire damage to attacks should ever appear on your weapon, gloves, or rings.

The reason is purely mechanical. These affixes let Oil Grenade apply its own, much weaker, ignite, which overwrites the one from Flameblast instead of relaying it. Your damage collapses and nothing in the interface points to the cause. A good 40-exalted ring can cost you half your power this way.

If you really want to keep a piece with this affix, there’s a workaround: slot Elemental Focus into Encroaching Ground, which stops the stray ignite from happening.

The Three Gear Tiers

The build comes in successive versions, each playable as-is. None is a mandatory stepping stone to the next.

Tier 1 — the 20-exalted starter. Life, armour, resistances, a +5 to fire spells staff. This is the version shown in T15 at level 60. It’s enough to clear a full Atlas.

Tier 2 — six divines, 225% rarity. Morior Invictus, Ingenuity to amplify the rings, the Nascent Hope charm, and above all jewels whose only mandatory affix is ignite magnitude — From Nothing already shows up at this tier. Flameblast becomes five-linked, Mana Remnants offsets the mana cost of Cast on Elemental Ailment. This version tanks a ten-remnant expedition without flinching, where other builds demand hundreds of divines for the same content.

Tier 3 — the zoomed-in Mageblood version. Cast on Dodge fixes the main complaint about early-league builds, their slowness. Loreweave, Darkness Enthroned and a Fox idol bring the quality that fuels the damage. From Nothing transforms the neighbouring notables, backed by Megalomaniac and Undying Hate; Josiah picks up Slow Burn, Firestarter and ignite magnitude there.

Beyond that, Benji’s endgame version sits around 1,000 to 2,000 divines for 329,000 effective HP and roughly ten million ignite DPS, with armour, evasion and deflection stacked — Cast on Dodge###UNTRANSLATED### conservé par-dessus.

Leveling and Switching to Flameblast

You don’t play this build from act one. For leveling, Josiah recommends Permafrost Bolts, grenades or twisters — whichever the game hands you first.

The switch becomes possible once two conditions are met: Advanced Thaumaturgy and 20% quality on your Flameblast. Technically that can happen before the end of the campaign. In practice, the author suggests waiting until you reach maps — the transition is smoother, and the gain before maps stays marginal.

What This Build Costs Your GPU

Let’s be blunt: burning grounds are heavy to render, and overlapping areas tank your framerate. This isn’t an occasional glitch — it’s inherent to how this build deals its damage.

The good news is that you can fix this yourself. The faster you move, the less the areas overlap, and the smoother things stay. The worst-case scenario is a player standing still, spamming Oil Grenade on the same spot. With a bit of practice, you learn to judge the distance and the delay before dropping another grenade, and framerate dips become far rarer.

Skill Tree