The "Soul" (ソウル Souru) is a special zone localized underneath each card on the field, which works as another resource for paying costs such as Soulguard, or to get effects as well. A card is always put into the soul face up unless otherwise specified, and while a card in the soul is face down, only the owner of that card can see what it is.
- When a card with soul leaves the field, all cards in its soul are sent to the drop zone. e.g. If Armorknight Succubus was put into Armorknight Cerberus' soul, Succubus' soul would be sent to the drop zone.
- When a card is put into a soul from the field, it is considered as "leaving the field".
- When a new monster enters the field "on top of" another monster by a card's cost or effect such as Jackknife Dragon's, the old monster and all cards in its soul will be put into the soul of the newly called monster. Said cost or effect must say "on top of" to make this possible.