The Sage of Time, known as Toki no Okina in Japanese, is most likely based on Father Time. The Japanese name translates into Time's Graybeard. This title was commonly attributed to the Greek Chronos or even Death itself.
He is the personification of time and appears as an elderly man, sometimes with wings, dressed in a robe and tends to carry either a scythe, an hourglass or other timekeeping device (which represents time's constant one-way movement, and more generally and abstractly, entropy).
The wings and hourglass were early Renaissance additions and he eventually became a companion of the Grim Reaper, personification of Death, often taking his scythe. He may have as an attribute a snake with its tail in its mouth which could based on either an ancient Egyptian symbol of eternity or the Ouroboros itself.
The Sage of Time appears in an optional battle during the evening of the 6th Day in an event called Wielder of Time, luring civilians using hypnosis so that he and his fellow demons can eat their souls. During the battle, the player must defeat the Sage of Time while preventing the civilians from being eaten or killed.
When any team leader is next to a hypnotized civilian, they are able to break the civilian out of the Sage's hypnosis, causing them to flee the battlefield rather than walk towards the Sage. Over time, more hypnotized civilians will also enter the battlefield. At the Sage's death, the demons following him will flee.
Devil Survivor 2
"A grim reaper of sorts. The hourglass in his hand governs time and controls the lifespan of man. He does not kill for fun, but rather comes when a person's time is finished. His hourglass is absolute, but if you can somehow flip it over, you can reverse the sands of time."
—Devil Survivor 2 compendium
The Sage of Time appears on the 2nd Day during New Game Plus in the Father Time event. He attacks the protagonist's party in Osaka, at the Sankyu Line. He also summons several unique demon teams to aid him, including Pazuzu, Yama, and Scathach. If the battle drags on for long enough, he will also begin to use his ability to have all enemy teams gain turn speed to put more pressure on the player. Should he also defeat a team, he will buff one enemy team and grant them increased turn speed.
Should the player challenge him with very few high-level demons in tow to make the battle a breeze, protection from Phys and Curse are incredibly helpful. The Sage of Time prefers to use his three attacks to petrify the player's teams with Petra Eyes and annihilate them with Death Call, failing that he will resort to a normal attack augmented by Attack All. His Holy Dance is only a problem if he gets an Extra Turn.
Defeating him earns the player the Soul Preserver title and the ability to fuse him in the Cathedral of Shadows. He can only be obtained by fusing Orthrus with Odin.