This guide contains story spoilers for the original campaign and Iron Marines Invasion, including final-boss identities and mission conditions.
Fast answer
The answer before the background
The original game contains three main bosses: Fell Tyrant on Sagan-1, MR: Rob070 on Ascendaar, and Nexus on Borealis. Fell Bishop and Overseer are high-threat minibosses. Invasion adds Void Prowler, Aart Ruin, Void Sovereign, Nexus, and Dark Herald. To win, preserve a durable unit to hold attention, focus damage on the boss or its required objective, clear summoned enemies before they surround your ranged units, and move whenever an attack marker appears. No reliable source documents unique boss loot drops; expect mission, achievement, credit, or Tech Point progress instead.
At a glance
Complete boss order and encounter conditions
The first game’s boss route follows the three campaign worlds. Fell Tyrant appears at the end of Sagan-1, MR: Rob070 is fought during Ascendaar’s Return of the Ascendii, and Nexus is the final boss of Borealis. The official store listing confirms 21 campaign missions across three planets, but it does not publish an official completion-time estimate. Your clear time depends heavily on difficulty, upgrades, heroes, and whether you replay Special Operations.
Iron Marines Invasion uses a larger galaxy and a different unit-selection system. The named boss roster includes Void Prowler, Aart Ruin, Void Sovereign, Nexus, and Dark Herald. Community records identify Aart Ruin in mission 21, Terminus, and Void Sovereign in mission 25, The Thing at the Doorstep. The publisher achievement list separately confirms objectives for the Void Prowler, Aart Ruin, Dark Herald, and the Raad Leader.
- Original first boss: Fell Tyrant, in Sagan-1 mission 8, War of Attrition.
- Original second boss: MR: Rob070, in Ascendaar mission 6, Return of the Ascendii.
- Original final boss: Nexus, in Borealis mission 7, From Beyond the Stars, commonly counted as campaign mission 21.
- Original minibosses: Fell Bishop and Overseer.
- Invasion bosses: Void Prowler, Aart Ruin, Void Sovereign, Nexus, and Dark Herald.
| Boss | Game and location | What starts the encounter | Best response |
|---|---|---|---|
| Fell Bishop | Iron Marines, Sagan-1 mission 7, Cocoon; also two Special Operations | Destroy the surrounding Cocoon before the creature can be fought normally. | Use a hero or durable melee unit to absorb pressure while Flamewalkers, Guardians, or other high-damage units attack. |
| Fell Tyrant | Iron Marines, Sagan-1 mission 8, War of Attrition | The final mission objective leads into the Tyrant fight. | Use Rocket Towers, Brawlers, Guardians, and Engineers; move units from the visible projectile impact zones. |
| MR: Rob070 | Iron Marines, Ascendaar mission 6, Return of the Ascendii | The final Ascendaar campaign mission brings the Peripheroid leader into battle. | Keep heavy units in front, concentrate fire, and avoid allowing supporting robots to split your force. |
| Nexus | Iron Marines, Borealis finale; also an Invasion boss | The final mission objective leads to a multi-phase elemental fight. | Interrupt or finish charging hands when possible, spread units, and destroy dangerous portals quickly. |
| Dark Herald | Iron Marines Invasion, late Dark Empyrean campaign | The final confrontation begins after reaching the Herald’s location. | Track teleport positions, remove Shades, and move squads away from crystal-spike warnings. |
Some fan-maintained lists call every large encounter a boss, while others classify Fell Bishop and Overseer as minibosses. This guide keeps the distinction used by the encounter descriptions: three main bosses in the original game, plus two minibosses.
Boss tactics
How to beat the difficult encounters
Fell Bishop is dangerous because it combines high durability, area damage, and a Cocoon phase. Clear nearby enemies before committing your main force to the Cocoon. Durable Guardians, a hero used as a controlled tank, and Flamewalkers are practical counters. Keep fragile Rangers and Snipers out of its attack area, because its swipe and corrosive projectile can punish tightly packed low-health units.
Fell Tyrant repeatedly shifts between above-ground and underground states. Its back cannons mark where projectiles will land, so do not leave squads standing on the target zones. The key practical rule is to keep damage flowing without chasing into danger. Rocket Towers are especially useful, while Brawlers can stay close and Guardians can reposition quickly. The Tyrant can recover part of the health lost during a phase change, so burst damage before it retreats is valuable. Bouncers are not a dependable counter because the encounter record states that they cannot damage it.
Against MR: Rob070, avoid turning the fight into several small skirmishes. Keep your army together, use the hero to intercept pressure, and focus fire on the boss whenever supporting machines are under control. This encounter is less about a single gimmick and more about preventing the Peripheroid army from overwhelming your ranged damage.
Nexus is the original campaign’s hardest mechanical check. Its hands charge elemental attacks, and the encounter description states that damaging a hand only stops the attack if you complete the required damage threshold. Split units enough to avoid losing the entire army to one effect, but do not scatter so far that healing, shields, or reinforcements become impossible. In the second phase, watch for the ray concentraters and EMP attacks. Destroy Raad Portals promptly when they begin producing Geon Enforcers, and avoid explosive plants around the arena.
- Use front-line units to hold boss attention while ranged units attack from a safe angle.
- Treat every visible attack marker as a movement command, not as decoration.
- Save orbital weapons, reinforcements, or hero abilities for a phase transition or summon wave.
- On higher difficulty, crowd control and shields are usually more valuable than adding another fragile damage dealer.
- If a fight feels impossible, replay earlier missions for hero experience, upgrades, and a better unit composition.
| Threat | Counter priority | Common mistake |
|---|---|---|
| Area damage | Spread fragile squads and use durable units first. | Stacking Rangers or Snipers beside the tank. |
| Summoned enemies | Kill the adds before returning to the boss. | Ignoring reinforcements until the back line collapses. |
| Boss retreat or phase change | Use burst damage during safe windows. | Chasing underground or through an active hazard. |
| Instant-kill warning | Move squads immediately; preserve the hero if the attack treats heroes differently. | Assuming a unit can survive because it has full health. |
The counters above are tactical recommendations based on the recorded attack patterns and unit roles. They are not mandatory team compositions, and exact effectiveness can change with difficulty, upgrades, hero level, and platform balance.
Invasion roster
All named Invasion bosses and enemies
Invasion’s enemies are organized around several factions, and each world introduces different pressures. The official site confirms that worlds have distinct terrain, enemies, and conditions. The complete named enemy records group the roster into Crimson Vultures, Dark Empyreans, and Raads, with the bosses listed separately.
Void Prowler is the early boss associated with the publisher’s timed achievement. Aart Ruin commands a giant mobile drill and can attack over barriers, so keep damage dealers positioned where obstacles do not block them. Void Sovereign uses multiple eyes with different effects and is listed as the third boss. Nexus returns as a Raad leader, while Dark Herald uses teleportation, Shades, and crystal spikes. The Herald’s crystal-spike phase is especially important because the recorded behavior says those spikes can instantly kill squads while leaving heroes unaffected.
- Crimson Vultures: Outlaw, Gangalorian, Mobster, Copter Mobster, Renegade, Hornet, Vor, Executioner, Typhoon, and Discharger.
- Dark Empyreans: Shade, Sinister, Strix, Nemesis, Infused Crystal, Void Wraith, Void Specter, and Domitor.
- Raads: Pyron Charger, Ion Trooper, Ion Sieger, Geon Executor, Charger Veteran, Quantum Invoker, Inactive Carrier, Ion Carrier, Pyron Carrier, Geon Carrier, and Quantum Carrier.
- Other recorded threats include faction-specific carriers, portals, and summoned units that can matter more than the boss during a phase transition.
| Invasion boss | Verified encounter detail | Practical counter |
|---|---|---|
| Void Prowler | The publisher lists an achievement for defeating one in under 10 minutes. | Use a direct, high-damage force and avoid wasting time on optional fights. |
| Aart Ruin | Mission 21, Terminus; uses a giant drill vehicle and attacks over barriers. | Advance damage units around obstacles and complete the barrier objective quickly. |
| Void Sovereign | Mission 25, The Thing at the Doorstep; its eyes provide different effects. | Prioritize exposed eyes or the active support effect, then return to the main target. |
| Nexus | A Raad leader who uses elemental attacks, portals, and phase-based hazards. | Interrupt charged attacks, destroy portals, and keep units away from plants and beams. |
| Dark Herald | Uses teleportation, summoned Shades, and lethal crystal spikes across phases. | Watch the arena, reposition squads early, and let the hero survive dangerous spike patterns when possible. |
Nexus is the original game’s final boss. In Invasion, community records list both Nexus and Dark Herald as bosses, while the publisher’s achievement names the Dark Empyrean Leader and Raad Leader separately. Because available references do not present a single official boss-order table, this guide avoids claiming that every platform displays the same final-boss sequence.
Rewards and completion
What bosses drop and what beating them unlocks
These games are mission-based real-time strategy titles rather than loot-driven boss games. I could not verify a unique weapon, armor piece, hero, or fixed currency drop assigned to each boss. The reliable reward evidence is progression-based: completing missions advances the campaign, and publisher achievement pages list boss-related achievements that can award credits or Tech Points.
For the original game, the documented Tyrant achievements include defeating it on Normal or Veteran and defeating it on Impossible. In Invasion, the achievement list includes the timed Void Prowler challenge, the Aart Ruin barrier challenge, the Dark Empyrean Leader challenge, and the Raad Leader challenge. If a store page, guide, or player video mentions a boss drop, treat it as a mission reward, achievement reward, or platform-specific event unless the game itself labels it as a boss drop.
There is no reliable official answer to how long the campaigns take to beat. The original game advertises 21 campaign missions and 21 Special Operations. Invasion advertises 25 or more campaign missions and many Special Operations. A first clear with exploration and failed attempts will take substantially longer than a replay focused only on campaign objectives.
- Verified reward type: campaign progress from completing the mission.
- Verified reward type: achievement progress, including credits or Tech Points in the publisher support record.
- Not verified: unique boss loot tables, drop rates, guaranteed equipment, or boss-exclusive heroes.
- For faster clears, prioritize the objective, use saved consumables at phase changes, and replay with a stronger hero rather than farming an unconfirmed drop.
| Question | Evidence-led answer |
|---|---|
| Do bosses drop unique items? | No unique boss-specific item drop is reliably documented in the available official sources. |
| What is the first boss? | Fell Tyrant in the original game; Void Prowler is the first named Invasion boss in the commonly used roster order. |
| What is the final boss? | Nexus is the original campaign’s final boss. Invasion has both Nexus and Dark Herald as late named bosses, and the available references do not give one unambiguous official order. |
| How long does it take to beat? | No official completion-time estimate is published. Mission count and difficulty are documented, but playtime varies widely. |
Reward claims are intentionally conservative. The available references verify achievements and campaign structure, but they do not provide a complete boss loot table or a universal completion-time estimate.
FAQ
Common questions
How do I beat the Fell Tyrant?
Build Rocket Towers during the final stage, keep Brawlers or Guardians close enough to deal sustained damage, and move every unit out of the marked projectile zones. Attack during the above-ground window, then regroup rather than chasing underground. Avoid relying on Bouncers, which are recorded as unable to damage this boss.
How do I beat Bishop?
Destroy the Cocoon first, clear the surrounding enemies, and use a durable hero, Guardians, or Flamewalkers to hold the Bishop while ranged damage works from behind. Keep fragile units spread out because the swipe and corrosive area attack punish clumps.
Is Overseer a boss or an enemy?
Overseer is best treated as a miniboss. It is a high-threat flying Peripheroid with homing missiles, area melee damage, and the ability to retreat. Brawlers, Guardians, Shellstorms, and Diplomats are more dependable than fragile long-range units placed far away.
What is the Iron Marines final boss?
Nexus is the final boss of the original Iron Marines campaign, fought in the Borealis finale. It uses charged elemental attacks, portals, knockback, and later beam and EMP hazards.
Are there boss drops in Iron Marines Invasion?
No fixed boss loot table is verified by the available official references. The documented rewards are mission progress and achievements that can grant credits or Tech Points. Do not farm a boss expecting a specific item unless the game’s own reward screen confirms it.
Sources
What we checked
Official listings establish current availability and product facts. Community pages are used for mechanics and build history, then labeled separately.
- OfficialIron Marines official Steam store page
- OfficialIron Marines official universe page
- OfficialIron Marines Invasion official site
- OfficialIron Marines Invasion achievements, Ironhide support
- CommunityBosses list, Iron Marines Wikia
- CommunityFell Tyrant reference, Iron Marines Wikia
- CommunityFell Bishop reference, Iron Marines Wikia
- CommunityOverseer reference, Iron Marines Wikia