the Keeper of the Gate

Plutarch, On Isis and Osiris 364f
They call Dionysos up out of the water by the sound of trumpets, at the same time casting into the depths a lamb as an offering to the Keeper of the Gate.

Hyginus, Astronomica 2.5
Those who wrote the Argolica give the following reason for the constellation Corona. When Liber received permission from his father to bring back his mother Semele from the Lower World, and in seeking a place of descent had come to the land of the Argives, a certain Hyplipnus met him, a man worthy of that generation, who was to show the entrance to Liber in answer to his request. However, when Hypolipnus saw him, a mere boy in years, excelling all others in remarkable beauty of form, he asked from him the reward that could be given without loss. Liber, however, eager for his mother, swore that if he brought her back, he would do as he wished, on terms, though, that a god could swear to a shameless man. At this, Hypolipnus showed the entrance. So then, when Liber came to that place and was about to descend, he left the crown, which he had received as a gift from Venus, at that place which in consequence is called Stephanos, for he was unwilling to take it with him for fear the immortal gift of the gods would be contaminated by contact with the dead. When he brought his mother back unharmed, he is said to have placed the crown in the stars as an everlasting memorial.

Pausanias, Description of Greece 2.37.1-3; 2.37.5-6
At this mountain begins the grove which consists chiefly of plane trees, and reaches down to the sea. Its boundaries are, on the one side the river Pantinos, on the other side another river, called Amymane, after the daughter of Danaus. Within the grove are images of Demeter Prosymne and of Dionysos. Of Demeter there is a seated image of no great size. Both are of stone, but in another temple is a seated wooden image of Dionysos Saotes (Savior), while by the sea is a stone image of Aphrodite. They say that the daughters of Danaus dedicated it, while Danaus himself made the sanctuary of Athena by the Pontinos. The mysteries of the Lernaeans were established, they say, by Philammon. Now the words which accompany the ritual are evidently of no antiquity and the inscription also, which I have heard is written on the heart made of orichalcum, was shown not to be Philammon’s by Arriphon. I saw also what is called the Spring of Amphiaraus and the Alcyonian Lake, through which the Argives say Dionysos went down to Hell to bring up Semele, adding that the descent here was shown him by Palymnos. There is no limit to the depth of the Alcyonian Lake, and I know of nobody who by any contrivance has been able to reach the bottom of it since not even Nero, who had ropes made several stades long and fastened them together, tying lead to them, and omitting nothing that might help his experiment, was able to discover any limit to its depth. This, too, I heard. The water of the lake is, to all appearance, calm and quiet but, although it is such to look at, every swimmer who ventures to cross it is dragged down, sucked into the depths, and swept away. The circumference of the lake is not great, being about one-third of a stade. Upon its banks grow grass and rushes. The nocturnal rites performed every year in honor of Dionysos I must not divulge to the world at large.

Clement of Alexandria, Exhortation to the Greeks 2.30
Dionysos was anxious to descend into Haides, but did not know the way. Thereupon a certain man, Prosymnos by name, promises to tell him; though not without reward. It was a favour of lust, this reward which Dionysos was asked for. The god is willing to grant the request; and so he promises, in the event of his return, to fulfil the wish of Prosymnos, confirming the promise with an oath. Having learnt the way he set out, and came back again. He does not find Prosymnos, for he was dead. In fulfilment of the vow to his lover Dionysos hastens to the tomb and indulges his unnatural lust. Cutting off a branch from a fig-tree which was at hand, he shaped it into the likeness of a phallos, and then made a show of fulfilling his promise to the dead man. As a mystic memorial of this passion phalloi are set up to Dionysos in cities. ‘For if it were not to Dionysos that hey held solemn procession and sang the phallic hymn, they would be acting most shamefully,’ says Herakleitos.