What am I supposed to do in the tower?

Look at the paintings on the wall.

They show you periods from Zork's history.

But the paintings are more than pure information.

Because you're going to be experiencing some of that history.

Click on the hourglass in the center of the room.

And then sit in the chair that's revealed when you do.

Notice that you can rotate once you're in the chair.

Try spinning around a few times to see what happens.

Every time you spin counterclockwise, you go back in time, and every time you
spin clockwise, you go forward.

Look out the window to see what time you're in.

You might also find some useful objects out there.

One of them will give you water.

There's an icicle in the window of the Glacier Epozz (the earliest).

If only you had some way of taking it...

Try cutting it.

Use the saw from the time of the temple's construction.

Now the icicle will fall into the bowl.  All you need next is some way to
make it melt.

Things melt faster when they're really hot.

One of the eras seems especially hot.

Rotate into the Volcano Epozz, and the icicle will melt.