Slayers 2 orbs

In the game’s own item list, no boss is tied to an orb. All 9 art orbs come out of chests, and every one lists the same odds in the Archives: 2% from a world-boss chest, 1% from a common one. So the Reaper Orb, the Blood Manipulation Orb and the Dream Orb are farmed the same way: kill whatever drops the best chest you can reach, and open it. A patch could change that list; the place to check is the same screen in your own game, under Archives and Evil Art Orbs.

Archives, tab Evil Art Orbs (9). Reaper Orb, Common, and under Source: 2% from Ice Chest, Rare Chest, Sealed Cache T1, T2, T3 and World Events Chest, 1% from Common Chest and Lost Chest. Eight of the nine icons are padlocked for this player.

Frame at 9:43 of The ULTIMATE Level 1-225 Guide For ALL PLAYERS In Project Slayers 2!, recorded by Paradox — a player’s video, not an official image

A later clip at Lv 132: beating Mini Boss Thunder Trainee pays +108 Blood Manipulation Mastery and +10 Demon Progress, and leaves a Reaper Orb with a Claim prompt.

Frame at 4:40 of How To Become DEMON *FAST* In Project Slayers 2, recorded by BLUEZ — a player’s video, not an official image

Which chest, which boss

The chance is per orb: a 2% chest gives a 2% shot at a Reaper Orb, and separately at each of the other eight. The chest a boss leaves is printed on its health bar, so the right-hand column comes straight off the boss drop tables.

Chest	Chance per orb	One named orb in 10 chests	Who drops it
`Ice Chest`	2%	18%	Fujiko
`Rare Chest`	2%	18%	No boss bar on record shows this chest
`Sealed Cache T1`	2%	18%	No boss bar on record shows this chest
`Sealed Cache T2`	2%	18%	No boss bar on record shows this chest
`Sealed Cache T3`	2%	18%	No boss bar on record shows this chest
`World Events Chest`	2%	18%	Obari, Zentaro, Giyen, Saneri, Shinora, Tengai, Rengu, Nezura, Datai, Gyutai, Domae, Akazo, Sumari
`Common Chest`	1%	10%	Water Trainee Sabito, Stone Trainee, Thunder Trainee, Mother Bear
`Lost Chest`	1%	10%	No boss bar on record shows this chest

The 10-chest column assumes each chest rolls on its own, with no pity counter. None has been shown on screen.

Best farm on paper

Any of the 13 world bosses: a World Events Chest at 2% per orb, twice the rate of the mini bosses’ Common Chest. The drop calculator works for orbs too: type 2 into its chance box and read off how many kills a coin flip takes.

Not on any bar yet

Yahari and Reaper only show Come back at night by day, so their chest is unknown. Players describe sealed caches lying around the map and a Lost Chest after the Lost Slayer in Final Selection, but neither has been caught on screen with its label.

The 9 orbs and what the game says about each

Names are as the game spells them, including Pyrokenesis. The Ice art’s orb is the Cryokinesis Orb. Every entry is rarity Common and carries the chest list above. The time under each opens Paradox’s recording at that entry.

The Archives menu with the Blood Manipulation Orb selected, showing the same source list — The same screen two seconds earlier on `Blood Manipulation Or…` (the name runs off the panel). The `Source` list under it is identical to the Reaper Orb's.
Frame at 9:39 of *The ULTIMATE Level 1-225 Guide For ALL PLAYERS In Project Slayers 2!*, recorded by Paradox — a player’s video, not an official image

Blood Manipulation Orb
Starts Blood Manipulation core training · often searched as blood orb
“Half full of something that moves like blood and settles like it too. Crush it in a demon's hand to open Blood Manipulation core training.”
Archives entry at 9:39
Dream Orb
Starts Dream Manipulation core training
“A drowsy pulse moves inside. Crush it to open Dream core training, where sleep and flesh take the same shape.”
Archives entry at 9:41
Obi Manipulation Orb
Starts Obi Manipulation core training
“Something dark and silken coils inside. Squeezing it starts Obi Manipulation core training for an unclaimed demon core.”
Archives entry at 9:42
Reaper Orb
Starts Reaper core training
“Hollow as a little moon, it opens Reaper core training when squeezed by blood not yet pledged to an art.”
Archives entry at 9:43
Tamari Orb
Starts Tamari core training
“Warm and oddly heavy in the palm. Crush it to begin Tamari core training.”
Archives entry at 9:44
Shockwave Orb
Starts Shockwave core training
“Heavy in the palm, this orb starts Shockwave core training when crushed hard enough for the body to answer.”
Archives entry at 9:49
Arrow Orb
Starts Arrow core training
“Veined glass for an unbound demon core. Squeeze it to start Arrow core training, where force learns hidden direction.”
Archives entry at 9:51
Pyrokenesis Orb
Starts Pyrokinesis core training · often searched as Pyrokinesis Orb
“Heat crawls under the shell. Crush it to begin Pyrokenesis core training before the flame leaks away.”
Archives entry at 9:53
Cryokinesis Orb
Starts Ice Manipulation core training · often searched as Ice orb
“Frost beads beneath the shell. Squeezing it begins Cryokinesis core training for a core not yet claimed.”
Archives entry at 9:56

Which of these is worth farming for is a separate question: the art tier lists compare them, and Blood Demon Arts covers each art’s weapon and moves.

From chest to art

An orb does not hand you the art. Every description above says the same thing in different words: crush it to start that art’s core training. One run of that loop, filmed start to finish:

1 · Claim it
Kill the boss, open its chest, and walk up to the glowing orb. The prompt is the orb’s name with Claim on the T key. In the hero picture above, a Reaper Orb has just come out of a Thunder Trainee’s chest.
At night, one second before the next frame: an opened chest beside the player, two items on the grass, and the header Mini Boss Thunder Trainee Spawns in 1:56.
Frame at 4:39 of How To Become DEMON *FAST* In Project Slayers 2, recorded by BLUEZ — a player’s video, not an official image
2 · Hold it and click
The orb sits on your hotbar. Equip it and click it, and a quest titled <Art> Core Training appears in the tracker. The Shockwave version has 5 steps, in this order: Push ups, Barbell squats, Boulder Push, Boulder Split, Defeat Mizunotos (5).
The minigames are the ones breathing trainers use; the training guide explains each. The other eight arts’ lists may differ.
Shockwave Core Training 0/5: Push ups 0/1, Barbell squats 0/1, Boulder Push 0/1, Boulder Split 0/1, Defeat Mizunotos 0/5, each locked behind the one before. Reward line Exp +900 and Wen +405.
Frame at 5:22 of Project Slayers 2: FULL Demon Progression Guide (All Bosses), recorded by Deepshaken — a player’s video, not an official image
3 · Finish it
With the last step done, the art is yours at mastery level 1. Its further moves open in the skill tree as that mastery climbs, and the codes page lists a free skill-tree reset if you want to redo the points.
Training done: the chat reads You've proven yourself., the pickups +900 Exp and +405 Wen, a Shockwave NEW! notice, and Shockwave Mastery Lv 1 appears bottom right.
Frame at 6:18 of Project Slayers 2: FULL Demon Progression Guide (All Bosses), recorded by Deepshaken — a player’s video, not an official image

Two things that stop an orb

Leaving the server

Orbs from chests do not survive a rejoin. One player lost an Arrow Orb after logging off, another two Blood Manipulation orbs, and a reply in the first thread says every art orb goes when you leave. Use it in the session you find it.

Already having an art

Clicking an orb while you already have an art only gets “My power already runs in you” from Muzan, and the orb stays in your inventory. Reported in one thread and another. His line points at removing the current art first: Reset Evil Art in the shop, or the free ARTRESET code.

The other route: Muzan’s roll

Orbs are not the only way in. Once you are a demon, Muzan’s Give me your power rolls a random art in his lair, with a real chance of nothing. Chests are random too, but every boss kill is another roll, and you only crush the orb you actually want. Getting to Muzan at all is covered in how to become a demon and where to find him.