Guilds and Covens are organisations of Magic Users that share knowledge and resources. So what does a wizard need that a Coven or Guild ( hence forth guild ) can provide?

Library. Wizards who advanture or have money will collect volumes on the arcane and magical worlds that interest them. Any Guild will be well stocked with books on every subject from the mundane uses of majic to the mechanics of spell jammers. A guild may not have a focal point, in which case the books are kept with members who may loan them, or just allow others to read them.

Spell Components. A necessity for any wizard wishing to cast spells. DMs should allow the character to assume he has at hand the more common spell items needed if he is a member of a guild. More expensive or rare items can be purchased from the guild, who inturn have purchased excess from members. Guilds may also take orders for rare components from members or the members may in fact leave standing orders to be filled every month ( paid in advance of course ).

Level Training. If the DM chooses the advancement of a Magic User to the next level of experience may only signify the MUs readiness to gain the spells that accompany that level. In order to gains the spells that MU must study within the guild, time for testing and tutoring is given freely by members and those who do the training are designated by the Guilds head. training should take 1 week per level of spells being learned.

Hench men and Employees. Members of guilds may employee different hench man top perform differing tasks on their behalf. These may be lent between members , in the most common instance apprentices are loaned for the purposes in incantations. A guild may employ an agent who wil scout out potential henchmen or experts. See or Henchmen section for more.

Security. In a wizards absence his goods and tower are protected by the guild. Anyone attempting to comprimise a members tower will fall under the wrath of the combined guild. Likewise the guild will mediate any dispute between its members and non-members wizards and move to protect members being attacked by other guilds ( a mediation role is enforced here making the attacks stop with the threat of wider war ).

Combined Efforts. Guilds have greater resources when they work together. However the chance do do this is limited in AD&D as most spells are solo. But a guild can combine its strenght in one area which has fallen by the way side in recent years (due to pressure from weirdos) and that is the summoning of DEMONS. I have done out some rules here which you may find interesting and may add to your gaming experiance.

Guilds are organisations consisting of members, however that does not mean its leader is democratically elected. The mantel of leadership falls to the highest ranking wizards. In the case of a tie this is then and only then decided by vote. If the leadership of a guild is refused the refusing wizard may never be offered it again, unless circumstances absolutly demend it, and that only in the direst of circumstance.