So as the title says, when eternal soul is shuffled into the deck by castel's effect it does not destroy your monsters, which it should cause the card effect says "leaves the field".
As stated in the rulebook, "when a monster on the field is shuffled into the Main Deck, it is no longer a card on the field, however its effects that activate when it “leaves the field” will not activate", this has been ruled as the same as for Trap/Spells
The Mother Toast wrote:

This be the day of days! Rejoice my toasty brethren!