
The Presidents of the Goetia come from the Qlipha Samael. This Qlipha is the shell of Sephira Hod. The latter is ruled by the planet Mercury and therefore I summon the Presidents during Wednesdays.
In my magick with the Presidents of Goetia, I use the correspondences of Hod even for the Qlipha Samael:
Ruling planet: Mercury
Day: Wednesday
Astro hour: Mercury
Paper seal colour: orange
Plant: Orchid

Marbas

Marbas rules over 36 legions of Spirits. He can reveal hidden secrets to you. Also Marbas causes diseases and cures them (Marbas can be called upon for cursings). He gives knowledge in mechanical arts.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Read also about a healing spell for pets with Marbas and Heramael
Buer

Buer can teach you philosophy, the logical sciences, and also the properties of herbs and plants. Both the Goetia and the Daemonolatry Goetia tell us that Buer can heal all distempers in us (he heals addictions).
Buer can give you good advice about when to use magick and when to not. Moreover, Buer gives good Familiar servants. Finally, Buer rules over 50 legions of Spirits.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Read also about Buer and how he can heal depressions.
Botis

Botis can tell you about all things of the past and to come. He reconciles friends and enemies. Finally, Botis rules over 60 legions of Spirits.
Botis can help you to find new friends and show you the truth about your friends.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Marax

Marax can teach you astronomy and other sciences. He can also give you the knowledge about the properties of herbs and gems. He governs 30 legions of Spirits.
Source:
Goetia
Glasya- Labolas

Call upon Glasya-Labolas to keep your projects secret from your surroundings. Glasya-Labolas will keep you well informed about whats going on all around you.
Also, according to S. Connolly, we can call upon Glasya-Labolas for protection and execration magicks.
Source:
Daemonolatry Goetia by S. Connolly
Foras

Foras teaches all about herbs and gems. Also, Foras can help you to solve problems of a business nature.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Gäap

According to the classification list of the Spirits in Goetia, Gäap is classed as both Prince (Qlipha Gamchicoth) and President (Qlipha Samael).
This means that you can summon Gäap during both Thursdays and Wednesdays. Call upon Gäap to enhance your own magick and to make the magick of others weak.

Source:
Goetia & Daemonolatry Goetia by S. Connolly
Malphas

You can call upon Malphas almost as you would call upon Sabnock (for protection against psychic and magickal attack). I don’t think that Malphas will make your enemies sick, but Sabnock will.
Malphas will keep you well informed about the plans of your enemies and that which they have done against you. He gives good Familiar servants.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Read also about a protection spell with Malphas
Häagenti

Haagenti makes you wise and instructs you in various areas of your life. This Spirit can transform a not so good life situation into a better one.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Caim (Camio)

Camio can help you to know the truth about any given situation.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Ose

Ose makes you knowing in all sciences and helps you to know secrets. According to S. Connolly Ose can help us to learn a foreign language faster and also to upgrade our computer skills.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Amy

Amy can teach you astrology and other sciences. This Spirit can give you good Familiar servants and also teach you how to make/obtain magickal amulets.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Zagan

Zagan is both a King (Qlipha of Thagirion) and a President. Therefore, you can summon Zagan both during Sundays and Wednesdays.
This Spirit can help you heal your addictions and bad habits. He transforms a situation into its opposite.
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Volac

Volac can help you get unstuck in your studies and point you in the right direction. He can tell you where to seek treasure (I heard once that Volac helped a man to find a job).
Source:
Goetia & Daemonolatry Goetia by S. Connolly
Check out these posts about the Demons of Goetia:
The Earls of Goetia and how they can help you
The Marquises of Goetia and how they can help you
The Princes and Prelates of Goetia and how they can help you
The Dukes of Goetia and how they can help you
The Kings of Goetia and how they can help you
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