Même les dieux savent peu de choses sur lui. Il apparaît dans le monde de Pharasma sous la forme d'une gigantesque lune gibbeuse dévoilant un visage squelettique. Nul ne sait si la lune est le dieu, ou un simple reflet, plus petit du véritable Groétus. De plus, nul ne sait quel rôle exact jouera Groétus dans la fin du monde, ni quel est son lien avec Rovagug, une autre déité liée à la fin du monde.

Le volume 4 de la campagne de Shattered star en parle dans un de ses articles.

Groetus rarely appears in human form, but a few records from ancient Azlant describe him as a tall, slender man wearing a long gray-cowled robe that hangs heavily to the floor. He is slightly bent at the neck, as if bearing a great weight on his head, with ashen skin, hollow eyes, and long, smooth hands. His voice is the dry whisper of old paper, his laughter low and breathy, and his inflection archaic or foreign. His feet are bare and covered in soot and ash, like he has walked through an old fire for his entire existence. Groetus almost never intervenes directly in the mortal world, as if doing so were against some personal, self­ defined code. His few positive interventions have been on behalf of his prophets, granting them a few moments of clarity at a critical time when their madness would interfere with his intentions. When he is displeased, madness intensifies or magnifies, phobias are born or triggered, and eyes become cloudy or weep itchy gray f luid. Formal raiment for the church is usually a light gray robe with pale blue trim. The exact shade varies from region to region and prophet to prophet, but is always some form of gray with blue accents. Most priests put little stock in their appearance (after all, they are anticipating the end of all things), and their clothing tends to become shabby and stained as the years go by. Many priests allow their hair to grow long and unkempt, but some shave their heads and color around their eyes with dark blue paint or makeup to represent the dreaded skull-moon image of their strange god. Groetus is chaotic neutral, and his portfolio is empty places, ruins, and oblivion. His favored weapon is the heavy f lail-a deadly weapon evolved from a tool to thresh grain from chaff. Some worshipers suggest this represents the god's role of breaking the world at the end of all things to free the pure essence within ruined matter. His symbol is a full moon with the faint image of a skull seen in the pattern of craters that decorate its surface. His domains are Chaos, Darkness, Destruction, Madness, and Void. Most of his priests are clerics, though a few wizards, summoners, and oracles claim to be prophets of his word, and the true clerics of Groetus do not dispute these claims. He is called the God of t he End Times, the God of t he End of t he World, and the Harbinger of Last Days.

Despite their rampant madness and tendency to group in independent cells, the faithful of Groetus are united in celebrating one holiday. The Final Day: On the last day of the year, the faithful observe silent prayer for an hour at sundown, hoping for guidance from Groetus or a sign that the end times will come soon. Some cults follow this with other rituals such as sacrifices and chanting.