Nexus towers draw upon the life force of living beings, and use this energy to create mighty spells, or craft magic items in great numbers. It could be argued that it is the nexus tower that is primarily responsible for modern urban civilization, for the nexus towers are the reason most cities were created in the first place, and it is the nexus towers that continue to make these cities possible.
In general, a city has one nexus tower for each 100,000 to 300,000 inhabitants. If it had more, the magical emanations of the towers would interfere with each other's operation. If it had less, the nexus towers wouldn't be able to harvest the magical energies from all of its inhabitants.
Nexus Towers in OperationEach nexus tower generates a base number of one energy point each year for every ten living being with a Charisma of 3 or greater within its area of operation (usually a specific neighborhood of a city, although if a community is small enough, it might be the only nexus tower in it). This number is modified by the following conditions:
Strength of Life Energy Drain: The operators of the nexus tower can decide on drawing more life energy from the inhabitants of its vicinity than normal. Doing this is dangerous, however, as the people are starting to feel adverse effects from the drain. The following levels are possible:
- Slight Drain: The drain isn't noticeable for all but the most sensitive people, and any lost energy is soon replenished. The number of energy points generated is unchanged.
- Moderate Drain: The people in the area of operation are starting to feel apathetic. Anyone living there will loose one point of Charisma each month up to a maximum of -2. Moving away will cause the Charisma loss to regenerate at a rate of one point per month, but this loss cannot be healed through magical means except by a wish or miracle spell or equivalent. The number of energy points generated is multiplied by two.
- Severe Drain: It is hard to motivate the people who live in the area of operation to do anything other than their daily routine, and beings with a low life force will soon become catatonic and die. Anyone living there will loose one point of Charisma each month up to a maximum of -6. Moving away will cause the Charisma loss to regenerate at a rate of one point per month, but this loss cannot be healed through magical means except by a wish or miracle spell or equivalent. The number of energy points generated is multiplied by three.
- Deadly Drain: The pain everyone experiences in the area of operation as his life force is sucked out of his body is so intense that they can do little except eat and drink, and even that requires some effort. Anyone living there will loose one point of Charisma each month, and once their Charisma reaches 0, they will become catatonic and die unless tended to. Moving away will cause the Charisma loss to regenerate at a rate of one point per month, but this loss cannot be healed through magical means except by a wish or miracle spell or equivalent. The number of energy points generated is multiplied by four.
- No City Planning: The nexus towers are built more as an afterthought, or the builders didn't want to alter the city just for gathering more energy. Regardless, buildings and streets are located without any regard for the needs of the energy flows. The number of energy points generated is divided by four.
- Minor city planning: The major thoroughfares and a few public buildings are placed according to arcane principles, but nothing more than those. The number of energy points generated is divided by two.
- Normal city planning: All streets are placed according to the principles of mystical architecture, and most buildings have to be built according to certain height and basic shape requirements. The number of energy points generated is unchanged.
- Strict city planning: All building plans and sites have to be approved by a central authority, which demands specific requirements for the size and shape of the building, up to exterior ornamentation of the building. The number of energy points generated is doubled.
- Invasive city planning: The level of detail necessary to maintain this level of city planning demands exact strictures for the build of each room in every building. Regular inspections of each room are required to make sure that the furniture is placed in the right way. The number of energy points generated is multiplied by four.
Using Nexus TowersThe energy gathered within nexus towers can generally be used for two things: They can either be used to create magic items, or to cast epic spells. The persons who use the nexus tower for these jobs need to be within specially prepared chambers within the tower.
Creating Magic Items: If the nexus tower was created to support the manufacture of a certain type of magic item, the gathered energy can be used to pay for the XP cost normally associated with creating that item. One energy points can be exchanged for one XP in this way. All other requirements for creating magical items still apply.
Casting Epic Spells: If a spellcaster is within the tower's ritual chamber (usually located at or near the top of the building), he can cast epic spells (see the Epic Level Handbook for details) as if he had the Epic Spellcasting feat, even if he does not meet the prerequisites for this feat. Unlike normal epic spells, spells that require a nexus tower to function can be written down, copied, and learned by other spellcasters normally (the DC for the Spellcraft check to learn such a spell is 25). All other requirements for epic spells apply normally. A spellcaster has one epic spell slot for each full ten ranks in his Knowledge skill appropriate to his way of spellcasting (in other words, a spellcaster needs at least 10 ranks in his Knowledge skill to use this aspect of Nexus Towers at all). Only a single spellcaster can draw upon the energy of a nexus tower at the same time, but spellcasters in other nexus towers that are within line-of-sight of the first one can help with the spell as additional participants (see page 92 of the Epic Level Handbook), with each tower contributing an additional epic spell slot to the ritual. Drawing upon the energy of a nexus tower in this way costs 190 energy points for each epic spell slot used.
Building Nexus TowersFirst, someone who is skilled in both architecture and magic must determine the best spot for a nexus tower in a given locale, and work out the building plans for a tower that will gather the energies as efficiently as possible. The minimum time required for this is six months, and the DC is equal to 20 plus 2 for every Magic Item Creation feat and each Epic Spell seed that the tower supports (if the tower doesn't support a certain Item Creation feat or Epic Spell Seed, it cannot support the creation of this kind of magic item, or the casting of epic spells that use that seed). The architect must roll against this DC with his Knowledge (Arcana) or Knowledge (Architecture and Engineering) skill, whichever one is lower. If the neighborhood from which the tower is supposed to be drawing energy from is altered in any significant way (fires, earthquakes, mass destruction by an invading army and so on), the research is wasted and must be started anew.
If this roll is successful, the nexus tower can be built. It costs 50,000 gp times the DC to complete. This is the minimum amount of gold necessary - given the importance of nexus towers, most builders will invest large amounts of money into the tower's defenses. Additionally, the neighborhood surrounding the tower will often be redesigned to improve the flow of energy. The cost for this is highly variable.