Transdimensional Position Anchor

After spending 1 minute casting the spell, you and every creature you choose within 100 feet of you that you can see has their position marked by an invisible quantity of the gem dust. At any time during the duration of the spell, if you stop concentrating on the spell, you and the creatures you chose during the casting will be transported back to the positions they were at. This teleportation occurs even if the creatures have moved between dimensions. 

If the spell runs for its full duration, the spell fails. If the caster is not capable of concentrating on the spell ( dying or otherwise incapable of concentrating ) the spell will teleport the creatures. The caster can choose to drop concentration at any point after its initial cast.