There are six ascension keystones, dropped by the slayer monsters in the Monastery of Ascension:

v • d • e Monastery of Ascension
Slayer creatures	Rorarius  Gladius  Capsarius  Scutarius
Legiones	Primus Secundus Tertius Quartus Quintus Sextus
Keystones	Primus  Secundus  Tertius  Quartus  Quintus  Sextus
Signets	Regular  I  II  III  IV  V  VI Corrupted  I  II  III  IV  V  VI
Crossbow	Main-hand crossbow  Off-hand crossbow  Bolts  Shard
Miscellaneous	Ascension fragment  Fragment arrows  Fragment bolts  History of the Order  Order journal page  Ocellus
Money making	Gladii Rorarii

v • d • e Keys
Steel key ring keys	Ancestral  Battered  Brass  Crystal-mine  Dusty  Enchanted  Enchanted 2  Maze  Metal  New  Shiny  Shortcut  Weapon store (removed)  Wrought iron
H.A.M.	Bronze  Iron  Steel  Silver  Prison
Triskelion Treasures	Crystal triskelion  Fragment 1  Fragment 2  Fragment 3
God Wars Dungeon	Frozen  Armadyl  Bandos  Saradomin  Zamorak
Shade keys	Bronze  Red  Brown  Crimson  Black  Purple Steel  Red  Brown  Crimson  Black  Purple Black  Red  Brown  Crimson  Black  Purple Silver  Red  Brown  Crimson  Black  Purple Gold  Gold
Bone keys	Ghosts Ahoy  Shilo Village
Ascension Keystone	Primus  Secundus  Tertius  Quartus  Quintus  Sextus
Miscellaneous	Keepsake  Crystal  Tooth half  Loop half  Dragonkin  Strange teeth  Strange loop  Treasure Trails  Muddy  Prison (Prison Pete)  Prison (Troll Stronghold)  Sinister  Tarnished  Iron  Cell  House key  Magic path  Ranged path  Cavern  Columbarium (Shiny)  Saradomin  Zamorak  Small  To the Crossing (Birthday)  Guard's  First floor  Casket  Display cabinet (Dimension of Disaster)  Display cabinet (The Golem)