What happens to each [Gabumon - Bond of Friendship] at the end of the turn?" The first copys effect was used to digivolve into [Gabumon - Bond of Friendship] while your security stack had 1 or more cards in it, so [Gabumon - Bond of Friendship] will be deleted at the end of the turn
But it's sometimes better to wait until draw for this kind of effectif, for instance, the only red spell we care about is Bloodbraid Elf, and we'd love for opponents to throw a Bolt or Command at nothing
Several cards featured in Ursulas Return - including Ursula, Erics Bride and Diablo, Devoted Herald - feature the Shift keyword but allow players to avoid paying ink altogether, in exchange for players having to discard a certain type of card/s to pay to shift them in instead
I agree that all of these cards are weaker in cube, but to varying degrees
The additional booster pack in each will help you better suite yourself to any adjustments needed to help uncover the secrets of what lies beneath