Eratrin’s Spectral Shield

Give any willing creature the material component, and from it springs a ghostly dome of translucent force, 5 feet in diameter, with its color matching the quartz that spawned it. The shield is incapable of being passed by a living creature, but anything dead or simply inanimate passes through.

The shield starts with hit points equal to the (caster’s level + caster’s constitution modifier + wielder’s level + wielder’s constitution modifier). This can be replenished up to its original maximum by the caster expending a spell slot, which will add (twice the caster’s level + the caster’s base constitution).
When neglected, however, to the point of its destruction, the shield will explode in a 10 foot line following the direction of the final blow, regardless of the direction it came from. Any creature, including undead, must make a dex save equal to the caster’s spell save dc, each taking damage equal to the final blow on a failed save, and half that on a successful one.

At higher levels, each spell slot above first will add additional maximum hit points equal to (caster’s level + caster’s con mod + wielder’s level + wielder’s con mod) per slot level