On Zu's secrets

For starters, a spell from Zu:

Lesser Empyrean Theft

The caster reaches through a burning pyre to retrieve an amount of unstable Empyrean Flame. Instead of letting it rage freely, the flame can also be wielded as a weapon for one round per level of the spell, causing 2d6 HP damage; or hurled as a single projectile or several smaller ones, for a total 1d6 HP damage per level of the spell. Alternatively, the  gate into the Empyrean Realm itself can be shaped and used as a burning barrier by, for example, causing it to stretch across a corridor or cover the floor. A special vessel prepared with materials worth 200 Kon can act as a receptacle for the Empyrean Flame, holding it indefinitely. With a gem-encrusted stylus worth 100 Kon, the flame can be carved into a surface to create Exploding Runes.

Level 1                   everburning flame (torch-sized)

Level 2                   ball or blade of fire

Level 3                   pillar of fire

Level 4                   great pyre

Level 5                   firestorm

+2 levels                use without pyre

Critical success: a friendly (but not enslaved) fire elemental of [spell level] HD is summoned.

Critical failure: the caster is set on fire.

Double critical failure: a hostile fire elemental of 2nd-7th level appears.

Next, some underlying cosmology for Zu which I have to write up eventually anyway, so why not know?

My present and prospective players really, really should not read this.

Names have power. The world of Zu exists and continues to exist because its name gives it the power to do so. In legendary times, a group of heroes arose, carried out acts of legend which will go undiscussed for now, then taken upon themselves to act as stewarts and guardians of the known lands. To this end, they've adopted names which also carry the power of Existence, and rule to this day as the immortal deity-kings already named in an earlier post. Thanks to the power of Existence in their names, their domains continue to harbour human civilisation.

The Lowlands, however, are different. They are an ephemeral land where the landscape twists, disappears and recreates itself constantly, because the power of Existence is not present. Given a king with the right name, it too would settle down like its surrounding areas. Such a king, however, is unlikely to appear, as the Lowlands already have two secret contenders for rulership, and they're unlikely to tolerate a newcomer. Unfortunately, either contender gaining supremacy over the other would certainly make the land even less inhabitable as it is today.

One of the would-be rulers has a well-known name, even if very few people are actually aware of the entity behind it. That name winds through the land as slow and cold water, supporting and taking away life in equal measure. But underneath its namesake river lies the Olm, a titanic creature of blindness and hunger. It has no intelligence in a human sense, but sheer ancestral age has elevated it to a near-divinity that even the greatest sorcerers alive have no hope to match. Should it gain monopoly over the Lowlands, those would turn into a lightless freezing hell of silent, ever-hunting amphibian death.

Opposite the Olm lies another intelligence, as methodical and calculating as the other is instinctive, and just as inhuman. Adventurers know of the Dungeon, the great system of subterranean ruins and caves that allegedly runs beneath the whole stretch of the Lowlands. A few - mainly sorcerers - know that the mysterious entity Baratrón (commemorated in the Baratrón Pact and several other spells) lives at the deepest bottom of the Dungeon. Even fewer believe that Baratrón rules the Dungeon. And a handful might suspect that Baratrón is the Dungeon.

A long time ago, in a distant city state there was a pit into which criminals were thrown. Many died from the fall, but others lived on for hours or even days, broken of body and blinded by pain. They would curse the pit, the city, the people, the gods and all of existence, their souls finally departing them in a black and bitter cloud that would coalesce at the bottom of the pit and coat it with pain, spite and despair. One day, a small crack opened at the bottom of the pit, and started growing and growing over the years. It became a crevice, then a tiny chamber, a cave, a cavern - and eons later, there was the Dungeon, born of the execution pit of a forgotten city. It hates, it schemes, it lures in wizards with pacts and heroes with treasure, and it dreams of a time when the whole world will be a labyrinth of monsters, deadly traps and unloving corridors.

And while the Olm hungers and Baratrón schemes, wild heroes roam the surface. They strive against nature, beasts and each other. They love, hate and dream their heroic dreams that are dwarved by the two secret contenders' power, but which at the same time also tower above those. They are Men, and - for now, at least - the world is theirs.