Door Ward

A creature and nonmagical medium sized door of your choosing that you can see within range is enchanted with a magical link. The chosen creature gains a number of temporary health equal to the doors current hit points. If the creature would take damage; reducing the temporary health gained from this spell, then the door would lose that much hit points and every other creature effected by this spell would lose that much temporary health. The spell ends when the door is reduced to 0 hit points or 1 minute has passed. If this spell is casted using a 5th level or higher spell slot, then the doors damage threshold is taken into effect when damage is dealt to a creature's temporary health. Your DM has the ability to determine which doors can and can't be affected by this spell before its casting.

Using a Higher-Level Spell Slot. The number of creatures you can target increases by one for each spell slot level above 2.