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

 * Armorider Dragon Emperor, Suvarious
 * Duel Sieger "Spartand"
 * Ghoul Dragon Emperor, Adil Diablos
 * Gold Dragon, Abend
 * Martial Arts Dragon Emperor, Duel Sieger
 * Honor Emperor Dragon, Magic Gun Riki
 * Space Dragon Emperor, Galiazond
 * Wicked Dragon Emperor, Billion Knuckle

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

Size 3

 * Armorknight Iblis
 * Overlord Dragon, Valfares Blood
 * Super Combidragon, Brainbaltes

Size 2

 * Death Ruler, Vrykolakas
 * Purgatory Knights Leader, Demios Sword "Inferno"

Size 3

 * Hundred Demons General, Gokumengaiou

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, Kaiser Drum
 * Jackknife "Aggressor"
 * Jackknife "Anzestor"
 * Jackknife "Beistand"
 * Jackknife "Burn Energy"
 * Jackknife "Dispersal"
 * Jackknife "Jaeger"
 * Jackknife "Savior"
 * Jackknife "Thunder Storm"
 * Million Rapier Dragon
 * Systemic Dagger "Onca"
 * Takoyaki Loving, Drum
 * Thunder Knights, Drum Bunker Dragon
 * Ultimate Sword Dragon
 * Zweihander Dragon

Size 3

 * Armordeity, Dynamis
 * Dragon Knight, Geronimo
 * Dragon Knight, Spartax
 * Drum Bunker Dragon, "Dual Wield"
 * Fifth Omni Armored Dragon, Giant Battle Axe Dokuju
 * Fifth Omni Armored Dragon, Thousand Swords Yoko
 * First Crimson Chieftain, Greatest General
 * Iron Fortress Dragon
 * 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

 * Archdemon
 * Brave, Drum
 * Demon Lord, Joker Grunwald
 * 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

 * King the Dominator

Size 3

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

Size 2

 * Ghoul Deity, Gojinmaru
 * White Dragon Hermit, Nanase

Size 3

 * Sky Rush, Garyu-oh
 * Martial Arts, Oosumi

Size 2

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

Size 3

 * Deity of Sun and Death, Bloody King

Size 1

 * King of General Knowledge, Furcas

Size 2

 * Dragowizard, Gorgas
 * Great Commander, Dvorak
 * Great Duke, Astaroth
 * Super Tough! Asmodai

Other

 * Evil Deity Evil Demon, Goku Yamigedo
 * Great Fiend, Yamigedo
 * Resurrected Evil Deity, Yamigedo

Size 1

 * Code "CHOCO", The Baby

Size 2

 * Demonblaze, Maxwell
 * Fix Star, Astress
 * Jackknife "Override"
 * Jackknife, "Superior Plasma"
 * Giant Star, Leitning
 * Light Star Guardian, Jackknife "Astrel"
 * Line Legion, Safertier
 * Redshift, Spectrux
 * Railgun, E Magnerias
 * Sixth Omni Storm Lord, Variable Cord
 * Star Guardian, Jackknife

Size 3

 * Cosmic Storm, Greisen ZK
 * Cosmo Strada, Galaxias
 * Jackknife, "Superior Plasma"
 * Mega Particle, Aero Soul
 * Radiate Burst, Ganmaredius
 * Star Guardian, Jackknife "Full Burst"
 * The Law, Gairaplus

List of Cards that give Soulguard

 * Art of Heat Haze
 * Dragon Trust
 * Ultimate Buddy!

List of Anti-Soulguard Cards

 * Ninja Arts, Half-kill

Rulings

 * If a card is destroyed, but it is prevented from leaving the field with Soulguard, cards or abilities 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)