Every Fon service opens with Legba, and the reason is structural rather than sentimental. He is the one who can speak to all parties. In the account of his origin he is the youngest of the creator's children, given no department of his own but given instead every language, so that he alone can carry a message between his siblings and between the human world and theirs. A prayer sent to Sakpata or to Xevioso without Legba first is a letter with no postal service, and it is not that the other vodun refuse it, but that it does not arrive.
His position is the threshold. His shrine sits at the entrance to a compound, at the door of a market, at the meeting of paths, and it is typically a mound of earth rather than a carved figure, often with an erect phallus, sometimes with a pot, fed with palm oil and with offerings left where people pass. The phallus is not obscene in the Fon reading; it is fertility, potency and the capacity to open, and the discomfort it caused early European observers is a fact about them.
He is also the one who overturns things. Legba is a trickster in the strict sense: not a comic figure but a figure of disorder that is functionally necessary, who tests, who trips up, who exposes the gap between what people say and what they do, and who is therefore both indispensable and never entirely safe. Divination frequently sends a person back to Legba first, because an obstruction in a life is often understood as a gate that was not opened.