DefOrbit has five boss types with distinct combat mechanics. Bosses enter a more aggressive second phase at half health. In survival modes, bosses repeat with tougher cycles; the base HP below describes their first survival cycle. Campaign Expedition uses separate boss HP values adjusted for difficulty. Weapon recommendations apply to Campaign when you own that equipment; Classic and co-op use the Pulse Cannon.
Campaign Expedition ends each of its five sectors with a boss checkpoint, in the order shown below. Clear Sector 1 and The Phantom for Homing Darts, Sector 3 and The Crystalline for Plasma Burst, and Sector 5 and The Swarm Mother for Ricochet Bolts and Campaign Endless. See Weapons for tier stats and How to Play for Campaign progress and saves.
THE PHANTOM
Signature mechanic: Teleportation — Base HP: 15
BASE HP: 15
TELEPORT INTERVAL: 3s → 1.5s (PHASE 2)
The Phantom orbits at a fixed radius and teleports to a new random position. In the first survival cycle, its teleport interval falls from three seconds to 1.5 seconds at half health, with added positional jitter in Phase 2. It releases a radial spray of projectiles after teleporting, so track its new position and watch the incoming fire.
Strategy: Keep the Phantom in your firing arc and reposition as it teleports. In Campaign, Scatter Shot's spread can cover its new position; Plasma Burst can deal splash damage near an impact. Avoid assuming Homing Darts will track the boss: their automatic steering targets regular enemies. Watch for the radial spray and use your bombs to clear pressure during Phase 2.
THE SERPENT
Signature mechanic: Segmented body — Base HP: 18 (body) + 8 segments × 5 HP each
BASE HP: 18
SEGMENTS: 8 (5 HP EACH)
The Serpent is a multi-segment chain boss. Its main body leads a procession of eight trailing segments, each with their own health pool (5 HP each). Segments follow the head through the arena, forming a sinuous chain that becomes a wall of collision. Each time you destroy an individual segment, it spawns a "fang" — an autonomous turret that orbits and fires at the player, and these fangs grow more dangerous in Phase 2. Killing the head ends the fight entirely.
Strategy: Focus the head to end the fight quickly — killing the head finishes the encounter outright, so you never have to clear every segment. Plasma Lance excels here: its piercing shot at Tier III and above punches through the chain in a single bolt, hitting the head and multiple segments at once. Ricochet Bolts are similarly efficient, chaining hits down the body. Be aware that destroying segments spawns orbiting fangs, so if you cannot reach the head cleanly, expect fang turrets to appear — dodge their orbital paths and use Vortex Bombs if the fang count becomes overwhelming.
THE CRYSTALLINE
Signature mechanic: Splits into two children on death — Base HP: 20 / 10 / 5 (by generation)
GEN 0 BASE HP: 20
GEN 1 BASE HP: 10
GEN 2 BASE HP: 5
The Crystalline is an octahedral crystal boss that spawns two smaller versions of itself when killed — each child can split again once more, creating up to four Generation 2 fragments. The original boss fires periodic aimed projectiles; Generation 1 fragments move faster. Generation 2 fragments are small and fast but do not split or fire. The result is an encounter that starts as one target and ends as a coordinated swarm of fragments converging on Earth from multiple angles.
Strategy: Keep tracking the fragments after each split and stop them reaching Earth's shield. In Campaign, Scatter Shot helps cover fragments approaching from different directions. Use a Vortex Bomb when fragments cluster to damage several at once and clear nearby projectiles. Keep enough room to turn toward the next surviving fragment.
THE GUARDIAN
Signature mechanic: Rotating 234° energy shield — Base HP: 25
BASE HP: 25
SHIELD ARC: 234° (1.3π RAD)
SHIELD SPEED: 1.5 → 3 rad/s (PHASE 2)
The Guardian combines a base HP of 25 with a continuously rotating energy shield that covers 234 degrees — nearly two-thirds of its perimeter at any time. Projectiles that strike the shield are blocked entirely. In Phase 2 the shield rotation speed doubles to 3 radians per second, making the window to strike the unshielded arc very brief. The Guardian also fires aimed projectiles at the player throughout the fight.
Strategy: Watch the shield rotate and aim at the unshielded gap as it enters your firing line. Piercing and homing do not bypass the shield. The Pulse Cannon's steady fire helps you use brief openings; Campaign upgrades can increase its fire rate. In Phase 2, reposition to keep the gap in view and save a bomb for moments when incoming projectiles limit your movement.
THE SWARM MOTHER
Signature mechanic: Continuous minion spawning — Base HP: 30, up to 15 minions active
BASE HP: 30
MINION CAP: 15
SPAWN INTERVAL: 0.5s → 0.25s (PHASE 2)
The Swarm Mother does not move fast or hit hard — its danger comes from the constant stream of minions it spawns every 0.5 seconds, up to 15 active at once. In Phase 2 the spawn interval halves to 0.25 seconds and minion movement speed increases from 120 to 150 units per second. Ignoring the Swarm Mother to clear minions first is a trap — new minions replace the killed ones faster than they can be cleared.
Strategy: Focus fire on the Swarm Mother directly. Every second you delay killing it is two more minions entering the field. Use AoE weapons — Plasma Burst clears minion clusters with each detonation. Ricochet Bolts chain through minion groups while your aimed fire stays on the Swarm Mother. If minion density becomes critical, deploy a Vortex Bomb to reset the swarm count, then immediately redirect all fire to the Swarm Mother. Kill the source; the minions die with it.