Soulguard

"Soulguard" (ソウルガード Sourugādo) is a Keyword that allows cards to avoid leaving the field (destruction, returning to hand, ect.) at the cost of discarding a card from the soul of that card.

It is marked by the text: 

Size 3

 * All Out Fighter, Broken Gai
 * Armorider Dragon Emperor, Suvarious
 * Blue Ocean Overlord, Duel Jaeger
 * Colossal Ocean Chief, Duel Jaeger
 * Deity of Military Arts Fighting Leader, Duel Yeager
 * Duel Sieger "Spartand"
 * Ghoul Dragon Emperor, Adil Diablos
 * Gold Dragon, Abend
 * Great Sea Deity, Duel Jaeger "Seazalion"
 * Invincible Fist, Duel Yeager
 * Martial Arts Dragon Emperor, Duel Sieger
 * Ocean Champion, Duel Jaeger
 * Honor Emperor Dragon, Magic Gun Riki
 * Space Dragon Emperor, Galiazond
 * Steel Arms Unrivaled Chief, Duel Jaeger "Revolted"
 * Steel Fist Fighter, Strong Goh
 * Traditional Fighter, Oriental Joh
 * Wicked Dragon Emperor, Billion Knuckle

Size 3

 * Billion Knuckle, "Spirit of the Chief!"

Size 1

 * Armorknight Succubus

Size 2

 * Armorknight Archangel
 * Armorknight Cerberus
 * Dense Forest Dragon, Radica
 * Fighting Dragon Emperor, Demongodol Ark
 * Fighting Dragon, Demongodol
 * Steel-blooded Dragon, Gavaldine
 * Strong-armed Dragon, Iron Caesar

Size 3

 * Armorknight Iblis
 * Eighth Omni Deity Lord, Grangadez
 * INV Eighth Omni Deity Lord, Devilgadez
 * Overlord Dragon, Valfares Blood
 * Super Combidragon, Brainbaltes

Size 2

 * Death Ruler, Vroukalakas
 * Daredevil, "Soul Crusher"
 * First Knight of the Apocalypse, Gratos
 * Purgatory Knights Leader, Demios Sword "Inferno"

Size 3

 * Black-slashing Demon Dragon, Garnibael
 * Great Demonic Black Dragon, Archenemy
 * Hundred Demons General, Gokumengaiou
 * Messenger of Despair, Metameria
 * Twin Blade Black Dragon, Zalcandira

Size 2

 * Gratos "Destruction Blade!"

Items

 * Chieftain Fist, Dragogeneral

Size 1

 * Dragon Knight, Martell

Size 2

 * "Awakened" Fifth Omni Dragon Lord, Drum
 * Blue Sky Knights, Drum Bunker Dragon
 * Crimson Battler, Drum Bunker Dragon
 * Dragon Knight, Kojiro
 * Drum Bunker Dragon
 * Drum Bunker Dragon Father
 * Fifth Omni Dragon Lord, Crimson Drum
 * Fifth Omni Dragon Lord, Drum
 * Fifth Omni Dragon Lord, Drum the Punisher
 * Fifth Omni Super Dragon Lord, Kaizer Drum
 * Fifth Omni Sky Dragon Lord, Kaizer Drum "Roar"
 * INV Fifth Omni Dragon Lord, Hellfire Drum
 * Jackknife "Aggressor"
 * Jackknife "Anzestor"
 * Jackknife "Beistand"
 * Jackknife "Burn Energy"
 * Jackknife "Dispersal"
 * Jackknife, "Drum Bunker"
 * Jackknife, "Gewalt"
 * Jackknife "Jaeger"
 * Jackknife "Savior"
 * Jackknife "Thunder Storm"
 * Jackknife "Neo Gold Ritter"
 * Million Rapier Dragon
 * Pizza Party! Bal Dragon & Jackknife
 * Presence of Yearning, Bal Dragon & Jackknife
 * Shining Board Dragon
 * Systemic Dagger "Onca"
 * Takoyaki Loving, Drum
 * Thunder Knights, Drum Bunker Dragon
 * Ultimate Sword Dragon
 * Zweihander Dragon

Size 3

 * Armordeity, Dynamis
 * Careful-choice Steel Fire Dragon, Lord Sushiroad
 * Dragon Knight, Geronimo
 * Dragon Knight, Spartax
 * Drum Bunker Dragon, "Dual Wield"
 * Fifth Omni Armored Dragon, Giant Battle Axe Dokuju
 * Fifth Omni Armored Dragon, Thousand Dachis Yoko
 * Fifth Omni Super Cavalry Dragon, Hellfire Sword Doble
 * First Crimson Chieftain, Greatest General
 * Iron Fortress Dragon
 * Kazuchika Okada!!
 * Scorching Cavalry Dragon, Second Helios
 * Skyblue Dragon, Crystal Saber
 * Super Armordragon, Aura Sword Dragon
 * Super Armordragon, Buster Cannon Dragon
 * Super Armordragon, Drum Breaker Dragon
 * Super Armordragon, General Boldness
 * Super Armordragon, Vajra Blaster Dragon
 * Systemic Sword Dragon

Size 2

 * Bal Dragon, "Bal Burst Smasher!!"
 * Fifth Omni Cavalry Dragon, "Cavalry Dragon Arts, Seven Divine Execute!"

Size 3

 * Empty Thunder Vessel, Zodiac (Star Dragon/Legend)
 * Shining Twin Star, Zodiac (Star Dragon/Legend)
 * Trial Star Deity, Tierkreis (Star Dragon/Legend)

Size 2

 * Archdemon
 * Brave, Drum
 * Demon Lord, Joker Grunwald
 * INV Third Omni Water Lord, Dark Miserea
 * Legendary Warrior, Gao
 * Third Omni Water Lord, Miserea

Size 3

 * Brave of the Sun, Gao
 * Demon Knight of Destruction, Fold Break
 * Diamond Golem, Fluud
 * Hades Dragon Chief, Red Arrogant
 * Guardian Dragon of Demon Lord Castle, Deukruzar
 * Guardian Dragon of the Ruins, Meteor Rain
 * Master Skeleton
 * Tosa Hound, Cobalt

Size 3

 * Deukruzar, "Second Manifestation: Demonknight"

Size 3

 * King the Dominator

Size 3

 * Battle Poet, Thinking
 * Great Sword Deity, Kaizerion
 * Infinite Robo, Mathematics
 * Rescue Dragon, Forcearms
 * Steel Beast Battle Robo, Gaidenor

Size 3

 * Gaidenoh, "Steel Beast Explosive Battle Cry!"
 * Great Gun Deity, Tigerion, "Kaizer Sword Buster!"

Size 2

 * Ghoul Deity, Gojinmaru
 * Sword Beast of Delusion, Kunitsuna Onimaru
 * White Dragon Hermit, Nanase

Size 3

 * Martial Artist, Osumi
 * Revelation Tactitian, Kagan Dragon
 * Sky Rush, Garyu-oh

Size 2

 * Gojinmaru, "Fierce God Secret Art, Yasha Deity Dance!"

Size 2

 * Armored Dragon, Cuelebre
 * Destruction Demon, Razer Back
 * Valkyrie, Brilliant Brynhildr

Size 3

 * Deity of Sun and Death, Bloody King
 * Valkyrie, Future Lamenting Skuld

Size 1

 * King of General Knowledge, Furcas

Size 2

 * Dragowizard, Gorgas
 * Great Commander, Dvorak
 * Great Duke, Astaroth
 * Illusionist of Shadowgraph, Silhouette Joe
 * Manipulator of Shadowform, Silhouette Terry
 * Super Tough! Asmodai

Size 2

 * Asmodai, “Diabolical Sparta Teachings!”

Size 3

 * Silhouette Joe, "Illusion Shadow Dragons"

Other

 * Specter of Darkness Wasteland, O-Yamigedo
 * Evil Deity Evil Demon, Goku Yamigedo
 * Great Fiend, Yamigedo
 * Ruler of Hundred Demons, O-Yamigedo
 * Resurrected Evil Deity, Yamigedo

Size 1

 * Code "CHOCO", The Baby
 * Star Dragoner, Luminous Blue

Size 2

 * Demonblaze, Maxwell
 * Fix Star, Athtress
 * Future Dragon, Drum the Neo
 * Hold Star, Envelope
 * INV Sixth Omni Storm Lord, Catastrophe Cord
 * Jackknife "Full Liberate Cannon!"
 * Jackknife, "Neo Aggressor"
 * Jackknife "Overwrite"
 * Jackknife, "Superior Plasma"
 * Jackmodai Aspires to be a Star Dragoner
 * Giant Star, Leitning
 * Radiant Guardian, Jackknife "Aster"
 * Line Legion, Safer Tear
 * Red Shift, Spectrums
 * Railgun, E Magneliaz
 * Sixth Omni Storm Lord, Variable Cord
 * Star Dragoner, Heliopause
 * Star Dragoner, Jackknife
 * Star Dragoner, T Alpha
 * Star Guardian, Jackknife
 * The Genesic, Omega Big Bang

Size 3

 * Cosmic Storm, Greisen ZK
 * Cosmo Strada, Galaxias
 * Four Quasar, Stein Cross
 * Jackknife, "Superior Plasma"
 * Mega Particle, Aero Soul
 * Radiate Burst, Gamma Radius
 * Star Guardian, Jackknife "Full Burst"
 * Star Dragon of Bonds, Jackknife
 * The Law, Gairaplus
 * The Over, EX Dimension

Size 2

 * Jackknife, "Astro Guardner!"

Size 3

 * Jackknife, "EXAM STYLE"

List of Cards that give Soulguard

 * Art of Heat Haze
 * Dragon Trust
 * Heat Blade, Joker
 * On Fleek!
 * Ultimate Buddy!
 * Wish-fulfilling Jewel

List of Anti-Soulguard Cards

 * Ninja Arts, Half-kill

Rulings

 * Soulguard DOES NOT prevent a card from being destroyed. If a card is destroyed, but stays on the field by using Soulguard, it is still considered to be destroyed and effects that activate when that card is destroyed (such as Penetrate) will still be activated.
 * Cards with Soulguard may be used to pay for call costs or card effects that require cards on the field to be sent to the drop zone, such as the call cost of Fighting Dragon, Demongodol, or the cast cost of Castling. In this case, the cost is considered paid even if Soulguard prevents the card from being sent to the drop zone.(Source)