Getting boss summoning items and ingredients.

Troll Idol:
    Desert Shell dropped from Sand Golem.
    Rammerhead Hide dropped from Rammerhead.

Explosive Idol:
    Dropped from Diocuses in the Precasian Undeground Dens.

Nethengeic Callstone:
    Dropped from Nethengeic Beasts in Nethengeic Pits.

Ancient Orb:
    Dropped from Kaiyu in Kaiyu Temple.

Heavy Boulder:
    Dropped from Terradon in the Precasia.

Petals:
    Crafted at Petal Crafting Station from 5 different flower petals.

Call of the Drake:
    Pure Rain Stone dropped from Coralon.
    Pure Water Stone dropped from Sea Viper.
    Pure Coral Stone dropped from Amphibior.

Hive Chunk:
    Dropped from Parasects in the Barathos.

Silvro Coin:
    Bought from Professor.

Boulder Dash:
    Crafted at Charging Table from Heavy Boulder and Primordal Dust.
    
Book of Shadows
    Dropped from Apparition, Web Reaper and Shade.

Primordal Dust:
    Bought from Primordal Merchant.

Staring Eye:
    Dropped Flesh Eater in Flesh Temple.

Toy Gyrocopter:
    Bought from Toy Merchant.

Guardian's Eye:
    Dropped from Lelyetian Warriors and Lelyetian Casters.

Giant Crystal:
    Bought from Crystal Trader.

Haunted Idol:
    Darkly Powder is dropped Faceless Floater.
    Primed Ghoulasm is obtained by converting Ghoulasm at the Haunting Table.

Shroom Stone:
    Dropped from Fungik, Fungback and Fungung.

Voliant Heart:
    Dropped Voliant.

Mega Rune Stone:
    Mega Rune Fragments dropped from Bouncer, Eye Creature, 
    Paladin and Runicorn.

Observing Eye:
    Dropped from Visulon.

Vile Stone:
    Obtained by charging Uncharged Stone at Enigma Station.
    Uncharged Orb is dropped from Dweller in the Deeplands.

Ancient Ring:
    Obtained from Shyregem Ingot and Shyrestone 
    with a chance at the Ancient Altar.


Boss Summoming

Smash:
    Troll Idol, Hunter Level 12.

Corallus:
    Has a 2% chance to spawn when the player kills Amphibiyte. 
    Amphibiyte spawns inside Amphibiyte Caves, 
    which can be found on the beaches of the Overworld. Hunter Level 30.

King BamBamBam:
    Explosive Idol in The Nether. Hunter Level 23.

Nethengeic Wither:
    Nethengeic Callstone in The Nether. Hunter Level 65.

Tyrosaur:
    Bloodstone at Tyrosaur Altar in the Precasia.

Skeletal Army:
    Ancient Orb at Army Block in the the Precasia.

Rockrider:
    Heavy Boulder at Rockrider Shrine in The Haven.
    
Vinocorne:
    Petals at Vinocorne Altar in the Gardencia.
    
Dracyon:
    Call of the Drake at Dracyon Altar in the L'Borean.

Hive King:
    Hive Chunk at Hive Spawner in the Barathos.

Silverfoot:
    Silvro Coin at Silverfoot Altar in the Iromine.

Kror:
    Boulder Dash at Kror Altar in the Deeplands.

Shadowlord:
    Book of Shadows at Shadowlord Altar in The Abyss.
    
Primordal Five:
    Primordal Dust x9 at 8 Primordal Lamps and Primordal Shrine in the Dustopia.

Elusive:
    Staring Eye at Illusion Altar in The Abyss.

Baroness:
    Bloodstone at Baroness Altar in the Barathos.

Gyro:
    Toy Gyrocopter at Toy Box in the Celeve.

Graw:
    Guardian's Eye at Graw Altar in the Lelyetia.

Crystocore:
    Giant Crystal at Power Station in the Crystevia.

Bane:
    Haunted Idol in the Greckon.

King Shroomus:
    Shroom Stone in the Mysterium.

Four Guardians:
    Voliant Heart at Guardian Altar in The Haven.

MechBot: 
    Bloodstone at MechBot Altar in the Iromine.

C.R.E.E.P:
    Explosive Gems at Greep Altar in the Creeponia.

Clunkhead:
    Mega Rune Stone at Clunkhead Altar in the Runandor.

Cotton Candor:
    Treat Bag at Candy Block in the Candyland.

Visualent:
    Observing Eye at Visualent Altar in the Lunalus.
    
Voxxulon:
    Vile Stone at Voxxulon Altar in the Vox Ponds.

Craexxeus:
    Ancient Ring at Craexxeus Altar in the Shyrelands.


A few notes:
    Tyrosaur, Baroness and MechBot will drop nothing.
    Cotton Candor immune to all damage except damage from basic staves: 
    Wind, Water, Fire, Poison, Wither and Noxious Staff 
    (depends on it's current bottom color).


Ancient Cavern Bosses

Coniferon:
    Selyan Shrine, 70 lvl Augury & Infusion.

Horon: 
    Luxon Shrine, 70 lvl Augury & Runation.

Penumbra:
    Erebon Shrine, 70 lvl Augury & Hunter.

Goldorth:
    Pluton Shrine, 70 lvl Augury & Foraging.
