The Shard of Eternity

From the introduction:

The tower of Elisan The Archmage rests in the doomed wasteland. A long time ago, a star from the sky fell right at the top of it, but the tower survived the explosion, protected by some mysterious bubble. This bubble saved the tower itself, while all the surrounding lands turned into the wasteland by a big explosion and now are haunted by ghosts. The legend tells that the tower is protected by the powerful artifact - The Shard of Eternity – which is hidden somewhere inside. Following the order of Elisan, the Shard summoned bubbles around the tower and all sentient beings inside it. The legend also tells: “Only a creature stupid enough can go to the tower to retrieve the artifact.”