I had a look with Near Infinity, and apparently that scroll is only available in one place in the game: It's sold by Orrick in Kuldahar.
But it's not among the items he sells in chapter 1 – it's added to his store when you return to him in a later chapter. (Chapter 2 I think, but I'm not entirely sure I'm interpreting that correctly in Near Infinity.)
PS: Of course when you're a Sorcerer, you could just learn the spell on level-up when you reach level 4...
The way Orrick's store is represented in the game files is kinda confusing, that's why I said I wasn't sure earlier. For starters, there are 4 different store files that are called "Orrick's Study":
Furthermore, the area script "AR2100.BCS" for the Kuldahar outdoors map has the following code which seems to add spells - including Decastave - to "KUORK0.STO" in chapter 2 and 4:
IF Global("UNIORRIK","AR2100",0) GlobalGT("Chapter","GLOBAL",1) THEN RESPONSE #100 SetInterrupt(FALSE) SetGlobal("UNIORRIK","AR2100",1) AddStoreItem("KUORK0","SPWI319X",1,1) // Lance of Disruption AddStoreItem("KUORK0","SPWI422X",1,1) // Mordenkainen's Force Missiles AddStoreItem("KUORK0","SPWI423X",1,1) // Shout AddStoreItem("KUORK0","SPWI424X",1,1) // Vitriolic Sphere AddStoreItem("KUORK0","SPWI517X",1,1) // Contact Other Plane AddStoreItem("KUORK0","SCRL6Z",1,1) // Phantom Blade AddStoreItem("KUORK0","SCFEAR",1,1) // Emotion: Fear AddStoreItem("KUORK0","SCSPIR",1,1) // Spirit Armor AddStoreItem("KUORK0","SCRL6M",1,1) // Enchanted Weapon AddStoreItem("KUORK0","SCRL6P",1,1) // Minor Sequencer AddStoreItem("KUORK0","SCRL6K",1,1) // Detect Illusion AddStoreItem("KUORK0","SCRL1J",1,1) // Invisibility, 10' Radius AddStoreItem("KUORK0","SCRL2A",1,1) // Monster Summoning II AddStoreItem("KUORK0","SCRL1S",1,1) // Dire Charm AddStoreItem("KUORK0","SCRL1O",1,1) // Slow AddStoreItem("KUORK0","SCRL1K",1,1) // Lightning Bolt AddStoreItem("KUORK0","SCDECA",1,1) // Decastave AddStoreItem("KUORK0","SCSNILL",1,1) // Snilloc's Snowball Swarm AddStoreItem("KUORK0","SCRLA3",1,1) // Glitterdust AddStoreItem("KUORK0","SCRL1D",1,1) // Clairvoyance AddStoreItem("KUORK0","SCRL69",1,1) // Charm Person AddStoreItem("KUORK0","SCRL1B",1,1) // Agannazar's Scorcher AddStoreItem("KUORK0","SCRL99",1,1) // Web AddStoreItem("KUORK0","SCRL96",1,1) // Mirror Image AddStoreItem("KUORK0","SCRL95",1,1) // Melf's Acid Arrow AddStoreItem("KUORK0","SCRL87",1,1) // Detect Invisibility AddStoreItem("KUORK0","SCRL92",1,1) // Know Alignment AddStoreItem("KUORK0","SCRL3G",1,1) // Vocalize AddStoreItem("KUORK0","SCRL83",1,1) // Chromatic Orb AddStoreItem("KUORK0","SPWI126X",1,1) // Expeditious Retreat AddStoreItem("KUORK0","SCRL81",1,1) // Sleep AddStoreItem("KUORK0","SCRLA6",1,1) // Spook AddStoreItem("KUORK0","SCRL79",1,1) // Shield AddStoreItem("KUORK0","SCRL77",1,1) // Magic Missile AddStoreItem("KUORK0","SCRL72",1,1) // Friends AddStoreItem("KUORK0","SCRL70",1,1) // Color Spray AddStoreItem("KUORK0","SCRL1E",2,1) // Dispel Magic AddStoreItem("KUORK0","WANDFRE",5,1) // Wand of Freezing Death AddStoreItem("KUORK0","WANDMIS",11,1) // Pemby's Wand of Many Missiles AddStoreItem("KUORK0","JASPER",4,1) // Jasper's Ring of Shocking Grasp AddStoreItem("KUORK0","ROGUE",1,1) // Rogue's Cowl AddStoreItem("KUORK0","SASH",1,1) // Shimmering Sash AddStoreItem("KUORK0","SCRCS05",1,1) // Scroll Case SetInterrupt(TRUE) Continue() END
IF Global("UNIORRIK","AR2100",1) GlobalGT("Chapter","GLOBAL",3) THEN RESPONSE #100 SetInterrupt(FALSE) SetGlobal("UNIORRIK","AR2100",2) AddStoreItem("KUORK0","SCRL6W",1,1) // Oracle AddStoreItem("KUORK0","SCRL6Z",1,1) // Phantom Blade AddStoreItem("KUORK0","SCRL5L",1,1) // Polymorph Other AddStoreItem("KUORK0","SCRLA8",1,1) // Contagion AddStoreItem("KUORK0","SCRLAJ",1,1) // Farsight AddStoreItem("KUORK0","SCRLA1",1,1) // Wizard Eye AddStoreItem("KUORK0","SCRL2H",1,1) // Shadow Door AddStoreItem("KUORK0","SCRL5T",1,1) // Protection From Electricity AddStoreItem("KUORK0","SCRL6Y",1,1) // Protection From Acid AddStoreItem("KUORK0","SCSTOR",1,1) // Ice Storm AddStoreItem("KUORK0","SCSHAD",1,1) // Shadow Monsters AddStoreItem("KUORK0","SCHMON",1,1) // Hold Monster AddStoreItem("KUORK0","SCSHRO",1,1) // Shroud of Flame AddStoreItem("KUORK0","SCDMS",1,1) // Demi-Shadow Monsters AddStoreItem("KUORK0","SCFEAR",1,1) // Emotion: Fear AddStoreItem("KUORK0","SCSPIR",1,1) // Spirit Armor AddStoreItem("KUORK0","SCRL6M",1,1) // Enchanted Weapon AddStoreItem("KUORK0","SCRL6P",1,1) // Minor Sequencer AddStoreItem("KUORK0","SCRL6Q",1,1) // Teleport Field AddStoreItem("KUORK0","SCRL6R",1,1) // Spider Spawn AddStoreItem("KUORK0","SCRL6N",1,1) // Fireshield (Red) AddStoreItem("KUORK0","SCRL1W",1,1) // Fireshield (Blue) AddStoreItem("KUORK0","SCRL6O",1,1) // Secret Word AddStoreItem("KUORK0","SCRL6J",1,1) // Spell Thrust AddStoreItem("KUORK0","SCRL6K",1,1) // Detect Illusion AddStoreItem("KUORK0","SCRL6L",1,1) // Hold Undead AddStoreItem("KUORK0","SCRL6I",1,1) // Protection From Cold AddStoreItem("KUORK0","SCRL6H",1,1) // Protection From Fire AddStoreItem("KUORK0","SCRL6G",1,1) // Minor Spell Deflection AddStoreItem("KUORK0","SCRL1J",1,1) // Invisibility, 10' Radius AddStoreItem("KUORK0","SCRL2A",1,1) // Monster Summoning II AddStoreItem("KUORK0","SCRL1S",1,1) // Dire Charm AddStoreItem("KUORK0","SCRL1O",1,1) // Slow AddStoreItem("KUORK0","SCRL1K",1,1) // Lightning Bolt AddStoreItem("KUORK0","SCDECA",1,1) // Decastave AddStoreItem("KUORK0","SCSNILL",1,1) // Snilloc's Snowball Swarm AddStoreItem("KUORK0","SCRLA3",1,1) // Glitterdust AddStoreItem("KUORK0","SCRL1D",1,1) // Clairvoyance AddStoreItem("KUORK0","SCRL69",1,1) // Charm Person AddStoreItem("KUORK0","SCRL1B",1,1) // Agannazar's Scorcher AddStoreItem("KUORK0","SCRL99",1,1) // Web AddStoreItem("KUORK0","SCRL96",1,1) // Mirror Image AddStoreItem("KUORK0","SCRL95",1,1) // Melf's Acid Arrow AddStoreItem("KUORK0","SCRL87",1,1) // Detect Invisibility AddStoreItem("KUORK0","SCRL92",1,1) // Know Alignment AddStoreItem("KUORK0","SCRL3G",1,1) // Vocalize AddStoreItem("KUORK0","SCRL83",1,1) // Chromatic Orb AddStoreItem("KUORK0","SPWI126X",1,1) // Expeditious Retreat AddStoreItem("KUORK0","SCRL81",1,1) // Sleep AddStoreItem("KUORK0","SCRLA6",1,1) // Spook AddStoreItem("KUORK0","SCRL79",1,1) // Shield AddStoreItem("KUORK0","SCRL77",1,1) // Magic Missile AddStoreItem("KUORK0","SCRL72",1,1) // Friends AddStoreItem("KUORK0","SCRL70",1,1) // Color Spray AddStoreItem("KUORK0","SCRL1E",2,1) // Dispel Magic AddStoreItem("KUORK0","SCRLA7",1,1) // Remove Magic AddStoreItem("KUORK0","MANTLEHF",16,1) // Mantle of Hell's Furnace AddStoreItem("KUORK0","OGI",1,1) // Ogi-Luc's Great Robe AddStoreItem("KUORK0","SCRCS06",1,1) // Scroll Case SetInterrupt(TRUE) Continue() END
Maybe there's a modder who has a better understanding of what's going on there?
Orrick's store is supposed to provide a scroll of Decastave in chapter 2 and a second scroll in chapter 4. Judging from a quick test the second scroll is only available if you purchased the first scroll before chapter 4. I would imagine this is true with other scrolls and items that are added twice as well.
The stores KUORK1.TO, KUORK2.TO and KUORK3.STO are most likely leftover files from original IWD which didn't support script actions that could add store items dynamically.
Summoned weapons, in general, are really powerful in Pillars of Eternity.
In the Infinity Engine games, summoned weapons are seldom better than the physical weapons you have access to at any given stage of the game, so it feels useless to expend spell slots for them.
Comments
But it's not among the items he sells in chapter 1 – it's added to his store when you return to him in a later chapter. (Chapter 2 I think, but I'm not entirely sure I'm interpreting that correctly in Near Infinity.)
PS: Of course when you're a Sorcerer, you could just learn the spell on level-up when you reach level 4...
that seems extremely likely
Maybe there's a modder who has a better understanding of what's going on there?
The stores KUORK1.TO, KUORK2.TO and KUORK3.STO are most likely leftover files from original IWD which didn't support script actions that could add store items dynamically.
In the Infinity Engine games, summoned weapons are seldom better than the physical weapons you have access to at any given stage of the game, so it feels useless to expend spell slots for them.