How does Trap The Soul interact with a Lich?

Question

Trap the soul forces a creature's life force (and its material body) into a gem.

It seems there's no description in the spell says if it would not work with an undead. So I assume it would just work for any undead and would trap their material body (with or without a soul).

But since a lich has already trapped its life force in a phylactery (so it does have life force that can be trapped by this spell), what would happen if it is affected by Trap the Soul? Would its life force be dragged from its phylactery into the gem?

An integral part of becoming a lich is creating a magic phylactery in which the character stores its life force.

Answer 1

You might be able to trap the lich

Neither the spell, nor the lich template has any language that clearly rules this out. The lich template says:

As a rule, the only way to get rid of a lich for sure is to destroy its phylactery. Unless its phylactery is located and destroyed, a lich reappears 1d10 days after its apparent death.

My take is that the spell fails unless the phylactery is nearby, because it has a range of close, and if the phylactery and with it the soul is out of range, targeting will fail. The targeting rules for spells say:

A spell’s range is the maximum distance from you that the spell’s effect can occur

Normally a creature is both body and soul, but in this case in particular where they are separated, it would seem important that the soul is in range.

Assuming both are in range, a DM who does not want it to work might also rule that imprisoning the soul is "a way to get rid of the lich", and therefore, it will reappear 1d10 days later (and its soul likely return to the phylactery), unless the phylactery is destroyed. But the more straightforward reading is that imprisonment is not death, and so thus could work.

I think this is a case where the rules need interpretation by the DM, who needs to decide if they want this to work, or not.