If one of the enchanted creatures leaves the battlefield without dying, Soulmates is put into its owner’s graveyard, but the other creature won’t be destroyed. The same is true if one of the enchanted creatures can’t legally be enchanted by Soulmates (perhaps because it gained protection from enchantments or it’s no longer a creature).
12-11-2019
wotc
If one of the target creatures becomes an illegal target while Soulmates is on the stack, Soulmates resolves but doesn’t enter the battlefield because its enchant ability won’t be satisfied. If both targets are illegal, it doesn’t resolve at all. In both of these cases, it’s put directly into its owner’s graveyard from the stack.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.