Transmortation

Touch a willing creature. That creature gains immortality for 24 hours. If the creature is killed within this time, it will immediately rise again in a form your DM finds appropriate (For example, if the creature falls into a vortex of fire in the elemental plane of fire, it will become a fire elemental, or a creature absorbed into a gelatinous cube becomes another gelatinous cube). The creature retains its personality, alignment, languages known (Your DM decides if it can still speak those languages), mental ability scores, and proficiencies. It also gains immunity to whatever killed it (How broad this is is up to your DM. for example, if the creature is swallowed by the tarrasque, than a lax DM may say that it gains immunity to acid damage, while a strict DM would say that it gains immunity only to acid damage dealt by being swallowed by the tarrasque).

When the spell's duration runs out, the creature automatically turns back to its original form, retaining its immunity, and gaining the ability to freely transform into whatever form it was in during the spell using an action. The effects of multiple castings of this spell do not stack, instead the new immunity and second form replace the old ones.