As two actions, you connect your life to that of a willing creature within 10 meters. While the target is within 10 meters of you, you have resistance to all damage. Also, each time you take damage, it takes the same amount of damage.
The spell ends if you drop to 0 health or if you and the target become separated by more than 10 meters. It also ends if the spell is cast again on either of the connected creatures. You can dismiss the spell on your turn (no action required).
You can expend 1 additional mana to target any creature within 10 meters which must succeed on a Will saving throw or be affected by this spell. Each time the target takes damage from this spell, it makes a new Will saving throw against the spell. If the saving throw succeeds, the spell ends.