diff --git a/sim/priest/items.go b/sim/priest/items.go
index 8355115210..4286104828 100644
--- a/sim/priest/items.go
+++ b/sim/priest/items.go
@@ -306,7 +306,6 @@ var ItemSetRegaliaOfTheCleansingFlame = core.NewItemSet(core.ItemSet{
 	Name: "Regalia of the Cleansing Flame",
 	Bonuses: map[int32]core.ApplySetBonus{
 		2: func(agent core.Agent, setBonusAura *core.Aura) {
-
 			// Fiend deals 20% extra damage as fire damage and cooldown reduced by 75 seconds
 			setBonusAura.AttachSpellMod(core.SpellModConfig{
 				Kind:      core.SpellMod_Cooldown_Flat,
@@ -412,5 +411,49 @@ var ItemSetRegaliaOfTheCleansingFlame = core.NewItemSet(core.ItemSet{
 	},
 })
 
+// T13 - Shadow
+var ItemSetRegaliaOfDyingLight = core.NewItemSet(core.ItemSet{
+	Name:            "Regalia of Dying Light",
+	AlternativeName: "Regalia of Dying light",
+	Bonuses: map[int32]core.ApplySetBonus{
+		2: func(agent core.Agent, setBonusAura *core.Aura) {
+			setBonusAura.AttachSpellMod(core.SpellModConfig{
+				Kind:       core.SpellMod_DamageDone_Flat,
+				ClassMask:  PriestSpellShadowWordDeath,
+				FloatValue: 0.55,
+			})
+		},
+		4: func(agent core.Agent, setBonusAura *core.Aura) {
+			priest := agent.(PriestAgent).GetPriest()
+
+			makeProcTriggerConfig := func(config core.ProcTrigger) core.ProcTrigger {
+				return core.ProcTrigger{
+					ActionID:       core.ActionID{SpellID: 105844},
+					Name:           "Item - Priest T13 Shadow 4P Bonus (Shadowfiend and Shadowy Apparition)",
+					Callback:       core.CallbackOnSpellHitDealt,
+					Outcome:        core.OutcomeLanded,
+					ProcChance:     1.0,
+					ClassSpellMask: config.ClassSpellMask,
+					ProcMask:       config.ProcMask,
+					Handler: func(sim *core.Simulation, spell *core.Spell, result *core.SpellResult) {
+						if priest.ShadowOrbsAura != nil {
+							priest.ShadowOrbsAura.Activate(sim)
+							priest.ShadowOrbsAura.SetStacks(sim, 3)
+						}
+					},
+				}
+			}
+
+			setBonusAura.MakeDependentProcTriggerAura(&priest.ShadowfiendPet.Unit, makeProcTriggerConfig(core.ProcTrigger{
+				ProcMask: core.ProcMaskMelee,
+			}))
+
+			setBonusAura.AttachProcTrigger(makeProcTriggerConfig(core.ProcTrigger{
+				ClassSpellMask: PriestSpellShadowyApparation,
+			}))
+		},
+	},
+})
+
 func init() {
 }
diff --git a/sim/priest/priest.go b/sim/priest/priest.go
index 19417bddd7..0187fe6258 100644
--- a/sim/priest/priest.go
+++ b/sim/priest/priest.go
@@ -20,6 +20,9 @@ type Priest struct {
 	ShadowfiendAura *core.Aura
 	ShadowfiendPet  *Shadowfiend
 
+	ShadowOrbsAura      *core.Aura
+	EmpoweredShadowAura *core.Aura
+
 	// cached cast stuff
 	// TODO: aoe multi-target situations will need multiple spells ticking for each target.
 	HolyEvangelismProcAura *core.Aura
diff --git a/sim/priest/shadow/TestShadow.results b/sim/priest/shadow/TestShadow.results
index 74c2b1e138..57e370d8ba 100644
--- a/sim/priest/shadow/TestShadow.results
+++ b/sim/priest/shadow/TestShadow.results
@@ -1226,6 +1226,13 @@ dps_results: {
   tps: 33728.8407
  }
 }
+dps_results: {
+ key: "TestShadow-AllItems-RegaliaofDyingLight"
+ value: {
+  dps: 35688.96997
+  tps: 31611.20778
+ }
+}
 dps_results: {
  key: "TestShadow-AllItems-RegaliaoftheCleansingFlame"
  value: {
diff --git a/sim/priest/shadow/shadow.go b/sim/priest/shadow/shadow.go
index 7fa59314cc..06756038da 100644
--- a/sim/priest/shadow/shadow.go
+++ b/sim/priest/shadow/shadow.go
@@ -51,9 +51,6 @@ func NewShadowPriest(character *core.Character, options *proto.Player) *ShadowPr
 type ShadowPriest struct {
 	*priest.Priest
 	options *proto.ShadowPriest_Options
-
-	shadowOrbsAura      *core.Aura
-	empoweredShadowAura *core.Aura
 }
 
 func (spriest *ShadowPriest) GetPriest() *priest.Priest {
@@ -110,7 +107,7 @@ func (spriest *ShadowPriest) ApplyTalents() {
 	})
 
 	// mastery aura
-	spriest.shadowOrbsAura = spriest.RegisterAura(core.Aura{
+	spriest.ShadowOrbsAura = spriest.RegisterAura(core.Aura{
 		Label:     "Shadow Orb",
 		ActionID:  core.ActionID{SpellID: 77487},
 		Duration:  time.Minute,
@@ -125,8 +122,8 @@ func (spriest *ShadowPriest) ApplyTalents() {
 				return
 			}
 
-			spriest.empoweredShadowAura.Deactivate(sim)
-			spriest.empoweredShadowAura.Activate(sim)
+			spriest.EmpoweredShadowAura.Deactivate(sim)
+			spriest.EmpoweredShadowAura.Activate(sim)
 			aura.Deactivate(sim)
 		},
 
@@ -136,7 +133,7 @@ func (spriest *ShadowPriest) ApplyTalents() {
 	})
 
 	spriest.AddOnMasteryStatChanged(func(sim *core.Simulation, oldMastery, newMastery float64) {
-		shadowOrbMod.UpdateFloatValue(getMasteryBonus(core.MasteryRatingToMasteryPoints(newMastery)) * float64(spriest.shadowOrbsAura.GetStacks()))
+		shadowOrbMod.UpdateFloatValue(getMasteryBonus(core.MasteryRatingToMasteryPoints(newMastery)) * float64(spriest.ShadowOrbsAura.GetStacks()))
 	})
 
 	empoweredShadowMod := spriest.AddDynamicMod(core.SpellModConfig{
@@ -145,7 +142,7 @@ func (spriest *ShadowPriest) ApplyTalents() {
 		FloatValue: getMasteryBonus(spriest.GetMasteryPoints()),
 	})
 
-	spriest.empoweredShadowAura = spriest.RegisterAura(core.Aura{
+	spriest.EmpoweredShadowAura = spriest.RegisterAura(core.Aura{
 		Label:    "Empowered Shadow",
 		ActionID: core.ActionID{SpellID: 95799},
 		Duration: time.Second * 15,
@@ -179,8 +176,8 @@ func handleShadowOrbPower(spriest *ShadowPriest, sim *core.Simulation, spell *co
 	if spell.ClassSpellMask&(priest.PriestSpellShadowWordPain|priest.PriestSpellMindFlay) > 0 {
 		procChance := 0.1 + float64(spriest.Talents.HarnessedShadows)*0.04
 		if sim.Proc(procChance, "Shadow Orb Power") {
-			spriest.shadowOrbsAura.Activate(sim)
-			spriest.shadowOrbsAura.AddStack(sim)
+			spriest.ShadowOrbsAura.Activate(sim)
+			spriest.ShadowOrbsAura.AddStack(sim)
 		}
 	}
 }
diff --git a/sim/priest/shadowfiend_pet.go b/sim/priest/shadowfiend_pet.go
index 007b423c29..48f372bc11 100644
--- a/sim/priest/shadowfiend_pet.go
+++ b/sim/priest/shadowfiend_pet.go
@@ -44,7 +44,8 @@ func (priest *Priest) NewShadowfiend() *Shadowfiend {
 
 	shadowfiend.DelayInitialInheritance(time.Millisecond * 500)
 	manaMetric := priest.NewManaMetrics(core.ActionID{SpellID: 34433})
-	_ = core.MakePermanent(shadowfiend.GetOrRegisterAura(core.Aura{
+
+	core.MakePermanent(shadowfiend.GetOrRegisterAura(core.Aura{
 		Label: "Autoattack mana regen",
 		OnSpellHitDealt: func(aura *core.Aura, sim *core.Simulation, spell *core.Spell, result *core.SpellResult) {
 			restoreMana := priest.MaxMana() * 0.03