Summoning in a nutshell:
For mages, it requires a Ritual Circle rated at least of the force of the spirit to be summoned and is defined by the type. A ritual ciricle is Force x meters in Radius. Circles may NOT cross each other. It takes Rating hours to draw a circle using chalk (5 nuyen per point) A higher rated circle may be used for summoning a lower rating spirit, mind you, the circle is just a protection against the reckless and unconditioned spirit. Addtionally, a material for the spirit to reside in is required relative to the force of the spirit (greater force = more material) Air elementals need burning incense or smoke, fire elementals an open flame, earth needs rock or clay, and water needs (relatively) clean water. You also need ritual materials which are random gew-gaws and expendables for the rituals, costing 1,000 nuyen per force. The magician must also have a Conjuring hermetic library available of at least the rating of the spirit (the cost of these is Rating^2x1,000 nuyen.
The ritual takes a number of hours equal to the spirit's force (Force 12 spirits are very hard to summon without lots of caffeine/stimulants) To successfully summon the spirit, the magician must perform the ritual as an Exclusive action, meaning no other spells may be directly sustained or cast during the ritual. The magician then rolls her Conjuring skill + any spirit focus or mage class advantage dice available. The magician can allocate conjuring dice to resist drain as well. The target number for this test is the Force of the spirit. If no successes are rolled, the spirit never arrives but all the ritual materials are used up (save the element used) The number of successes indicates how many services the Mage gets from the spirit.
Drain is then rolled, the damage level is variable based on the relation of the summoner's charisma rating and the force of the spirit:
Spirits Force is: Drain Level is:
1/2 of summoner's Charisma L
Summoner's Charisma or less M
Greater than Summoner's Charisma S
Greater than 1.5 x Summoner's Charisma D
If the spirit's force is greater than the summoner's magic rating, the drain does physical damage. In a healthy magician, this means summoning a force 8 Spirit usually leads to death. This drain is resisted with Charisma against a target number equal to the spirit's force.
If the conjurer is knocked out or killed the spirit becomes uncontrolled. Roll a Force (6) test for the elemental. If one success is generated, the spirit flees back to it's home metaplane. If none are generated the spirit goes berserk and starts combat with the nearest living thing using its powers to its fullest. It won't stop until killed, banished, or controlled by another mage.
Nature spirits follow this same pattern but instead of a lengthy ritual, they may be summoned on the fly without materials but their strength and utility is much less than that of an elemental. Summoning a nature spirit is a Complex action, using the same rules as above for Success test and Drain. Nature spirits never become berserk and simply disappear when uncontrolled. A nature spirit only lasts from dusk till dawn or vice versa. Therefore, summoning a spirit at 10 AM will allow you to use the spirit until Dusk (6-9PM variably) Any services left over are gone at this time.
To banish a spirit you roll your Conjuring skill + spirit foci or totem modifiers against the spirit's force using an Exclusive Complex Action (no spells sustained) and the spirit rolls it's force against the banishing magician's Magic attribute. Also, if the magician that is banishing the spirit is the spirit's summoner, they may add their Charisma to the dice rolled. If the banisher gets more successes, reduce the spirit's force by a number equal to the net successes. If the spirit wins, reduce the magician's Magic attribute by the net successes. After the first round of banishment, the winner gets to decide if the battle will continue. This is of course, provided neither the magician nor the spirit are disrupted.
If the spirit reaches 0 force, it is destroyed and is removed from both the physical and astral planes. If the banisher is reduced to 0 Magic, they pass out, taking deadly stun damage and must also check for Magic Loss. (Magic (Magic) test, failure = 1 lost Magic point)
Magic and Force lost in this manner recover at a rate of 1 per hour.