One by one.
In alphabetical order. Each one says what it does and what happens if you take more than one. Which ones are worth it: the item tier list.
Charged Perforator
10% of your hits call down a strong lightning bolt. Each extra one, more damage.
Stacking: Each copy adds the same, no cap.
Watch out: It deals 500% of the hit, not base damage. The strike is delayed and fast enemies can dodge it.
Defense Nucleus
Killing an elite spawns a strong robot ally that fights for you. Up to 4; each extra one, 4 more.
Stacking: Effective cap of 4 or 5 copies: there is a 20-ally limit.
Watch out: Engineer turrets do inherit it.
Empathy Cores
Every 30 s two robots come out to fight for you; they hit harder the more allies you have. Each extra one, more damage.
Stacking: Each copy adds the same, no cap.
Watch out: If Mithrix steals them, the probes come after you.
Encrypted Cerebellum
A quest item: it does nothing until you decrypt it.
Exposed Cerebellum
A quest item: you hand it to a powerful being in the game.
Faulty Conductor
Every 15 s, an electric wave gives you and allies more attack and movement speed. Each extra one, more often.
Stacking: The cooldown drops less with each copy.
Functional Coupler
You carry one more equipment and switch between them. Each extra one, another slot.
Stacking: No limit: each copy, one more equipment.
Watch out: If you lose it, you drop every equipment except the active one.
Genesis Loop
If you drop below 25% health, you explode and do massive damage around you. Recharges every 30 s; each extra one, sooner.
Stacking: Each copy lowers the cooldown (the game's «−50%» is not accurate).
Watch out: The 25% counts health plus shield. An unused Unstable Transmitter stops it from triggering.
Halcyon Seed
During the teleporter event, Aurelionite, a golden giant, appears on your side. Each extra seed, stronger.
Stacking: Aurelionite's health rises the same with each seed; its damage, less each time.
Watch out: Engineer turrets do not inherit it.
Irradiant Pearl
Raises everything by 10%: health, damage, speed, all of it. Each extra one, another 10%.
Stacking: Each copy adds the same, no cap.
Watch out: Not from printers or recyclers: only Cleansing Pools or a Shrine of Order.
Little Disciple
While sprinting, you fire wisps that chase enemies; the faster you go, the more you fire. Each extra one, more damage.
Stacking: Each copy adds the same, no cap.
Mired Urn
In combat, it tethers you to the nearest enemy: you drain its health and heal from it. Each extra urn, one more enemy.
Stacking: Each copy adds the same, no cap.
Watch out: It does not proc items, but its debuff counts for Death Mark. Only works in combat.
Molten Perforator
10% of your hits pull 3 lava balls out of the enemy that set things on fire. Each extra one, more damage.
Stacking: Each copy adds the same, no cap.
Watch out: It deals 300% of the hit, not of base damage (the game is wrong). Misses small enemies; great on big ones and bosses.
Mycelium Cap
No fall damage, and landing hard releases damaging spore clouds. Each extra one, more damage.
Stacking: Each copy adds the same, no cap.
Watch out: It cancels all fall damage. Clouds only spawn if the fall would have hurt.
Peace Flower
Only useful in one specific area: you use it to heal certain structures, and it hurts nearby enemies.
Watch out: The blast deals 1200%, not the 2000% the game says, and less with distance.
Pearl
10% more max health. Each extra pearl, another 10%.
Stacking: Each copy adds the same, no cap.
Watch out: Not from printers or recyclers: only Cleansing Pools or a Shrine of Order.
Planula
Every hit you take heals you 15. Great against lots of small hits. Each extra one, 15 more.
Stacking: Each copy adds the same, no cap.
Watch out: It heals before the hit lands, with damage over time and falls too; not with void fog.
Prison Matrix
50% more armour. Also goes into a specific terminal in the game.
Watch out: It only raises base armour, which most have at 0: it does nothing. Mercenary, REX, Loader, Acrid, Seeker and Drifter gain 10.
Queen's Gland
Every 30 s a beetle guard appears to fight for you. Each extra gland, another guard.
Stacking: Each copy adds the same, no cap.
Watch out: Engineer turrets do not inherit it.
Sentry Key
You move 15% faster. Also opens a specific terminal in the game.
Watch out: It cannot be scrapped.
Shatterspleen
Your crits cause bleeding, and enemies that die bleeding explode and hurt the ones around them. Each extra one, a stronger explosion.
Stacking: Each copy adds the same, no cap.
Watch out: It shares bleed with Tri-Tip Dagger. If the first crit kills, there is no explosion.
Titanic Knurl
More health (40) and faster healing. Each extra one, the same again.
Stacking: Each copy adds the same, no cap.
Watch out: Rejuvenation Rack multiplies its healing.
Whispering Fragment
Every 5 kills, a spirit joins you and fires alongside you a few times. Each extra one, one more time.
Stacking: Each copy adds the same, no cap.
Watch out: Always 5 kills, your own (not drones'). Spirits vanish at the end of the stage; 30 at most.
Other rarities: Common items · Uncommon items · Legendary items · Void items · Lunar items.