Plot Advice; Ask a simple question....

[Dust]

Just wrapping up the end of a well-received D&D game wherein the players are having a great deal of fun despite having misunderstood the overplot completely. I've been able to adapt so far and change things on the fly so that they weren't seen as completely incompetent, but there's a few loose ends that I need to address before the end of the campaign, in about....three game sessions.

There are rifts between the dimensions/planes opening up, and there are places in the world that seem to straddle the known planes. I need to explain how these dimensional rifts are a symptom of a long-slumbering lich demigod waking up.
Bonus points if you could also include a reason why the growth of the world tree could somehow stop these dimensional rifts, as well as cut off the lich from his demigod powers.

I promise it all made sense at one point. Oh, PCs.

[holywhippet]

Could it be a Demilich instead of a lich? The rifts could be opening up in locations where his/her soul gems are located.

Otherwise they could be opening up in locations where he has followers (dead or undead) or artifacts.

The world tree will block passage to anyone it doesn't like, the lich or his followers could be using it to gather power and they are bypassing it's defenses. If the tree grows it will be able to overcome the means they are using to travel along it.

[Winds]

The lich was attempting to leave this plane to another one, and was stopped. Or maybe he wanted to bring an outsider/number of outsiders here. Now that he's awakening, so are the spells he was using to do it. As to the world tree...it may have been used to seal him up, or the PCs need to somehow accomplish that effect. Alternately, growing the world tree strengthens the walls between realms, and makes it difficult/impossible to open these rifts.

[Bobby Archer]

Hmm, how about this:

The lich in question became a demigod largely through using an unusual phylactery, a small (minor, demi-, whatever) plane of existence. As the lich grew in power, the plane containing its soul also grew, pushing other planes into one another, the rifts being points of overlap.

In response to this, the world tree's roots began to wrap around and constrict the lich's soul-plane, eventually growing around it entirely, cutting it off from the lich. This caused the lich to fall into a slumber.

However, the soul-plane never stopped trying to grow out of the confines of its prison within the roots of the world tree. Recently, it has begun to succeed. As it expands beyond its prison, it once again pushes against the other planes, causing them to merge at these rifts. The renewed connection between the lich and its soul is causing it to awaken.

If the growth of the world tree can be spurred, it can once again begin to constrict and imprison the lich's soul-plane, cutting the lich off from its powers and closing the rifts by allowing the other planes to separate from one another.

[Odin the Ignoble]

Hmm, how about this:

The lich in question became a demigod largely through using an unusual phylactery, a small (minor, demi-, whatever) plane of existence. As the lich grew in power, the plane containing its soul also grew, pushing other planes into one another, the rifts being points of overlap.

In response to this, the world tree's roots began to wrap around and constrict the lich's soul-plane, eventually growing around it entirely, cutting it off from the lich. This caused the lich to fall into a slumber.

However, the soul-plane never stopped trying to grow out of the confines of its prison within the roots of the world tree. Recently, it has begun to succeed. As it expands beyond its prison, it once again pushes against the other planes, causing them to merge at these rifts. The renewed connection between the lich and its soul is causing it to awaken.

If the growth of the world tree can be spurred, it can once again begin to constrict and imprison the lich's soul-plane, cutting the lich off from its powers and closing the rifts by allowing the other planes to separate from one another.

I vote for this one. If only for an excuse to keep saying Soul Plane

[Dust]

Hmm, how about this:

The lich in question became a demigod largely through using an unusual phylactery, a small (minor, demi-, whatever) plane of existence. As the lich grew in power, the plane containing its soul also grew, pushing other planes into one another, the rifts being points of overlap.

In response to this, the world tree's roots began to wrap around and constrict the lich's soul-plane, eventually growing around it entirely, cutting it off from the lich. This caused the lich to fall into a slumber.

However, the soul-plane never stopped trying to grow out of the confines of its prison within the roots of the world tree. Recently, it has begun to succeed. As it expands beyond its prison, it once again pushes against the other planes, causing them to merge at these rifts. The renewed connection between the lich and its soul is causing it to awaken.

If the growth of the world tree can be spurred, it can once again begin to constrict and imprison the lich's soul-plane, cutting the lich off from its powers and closing the rifts by allowing the other planes to separate from one another.

You are my hero.