The Second Age is the period of time following the creation of Gielinor. During the slumber of Guthix, many Gods start to arrive on Gielinor, establishing territories and gaining followers. Many Gods would introduce their own races to Gielinor. It is known many more gods existed during the Second Age than today. The exact number is unknown but it may have exceeded twenty. These gods either allied with the more powerful gods on the plane during this time, perished during the God Wars that followed this age, or fled the plane during either period. This age could be considered one of the most important ages in the history of Gielinor, as many of beginnings of the feuds between the Gods and their followers can be traced back to this age.
The political structure of Gielinor during this age was dominated by the god Zaros, who was so influential that the Second Age could also be deemed the "Age of Zaros." Zaros founded the largest empire in the history of Gielinor during this age, and his highly aggressive means of expanding it made him feared by the gods that opposed him.
It is known near the end of the Second Age that the Staff of Armadyl fell into the hands of Zamorak after a series of events, and it was the key to his plans to betray Zaros. During his betrayal against Zaros, Zamorak stabbed Zaros with the staff, but Zaros did not fall, and they struggled until the staff pierced them both at the same time, when a part of Zaros' power flowed via the staff into Zamorak. After that, Zamorak became a god and Zaros was banished, locked in a distant and empty realm.
There is no known definite moment that marks Second Age's end, unlike some other ages. It could be considered to have ended abruptly with Zaros' banishment. Or it could have came to an end sometime after that, when the other gods, perplexed by Zamorak's ascension, banished Zamorak from Gielinor. What is known is by the time Zamorak returned, with an army behind him and declared war against all the other gods, much fighting had already broken out, triggering the Gielinorian God Wars, and the Third Age had begun.
- When Guthix entered his slumber, many gods arrived, or started appearing, on Gielinor.
- Tumeken, Elidinis and their children, Icthlarin and Amascut, founded the Kharidian/Menaphite empire in the modern Kharidian areas.
- Tumeken creates Het, Apmeken, Crondis, and Scabaras.
- The Duel Arena is built by followers of Het to train warriors.
- Zarosian Empire is established and immediately begins annexing territory. Throughout the Second Age, the empire extends rapidly through war and eventually becomes the largest and mightiest empire of Gielinor.
- Guthix's World Gate is sealed by the forces of Zaros, causing the Crystal seed supply from Seren's world to be cut off from the Elves.
- At some point, Zaros discovers the race that would come to be known as the Dragon Riders, and brings them from their world to Gielinor, where they become some of his most prominent and feared followers. However, due to their infertility - which remains uncured by Zaros - they are eventually depleted to only five in number by the time of Zamorak's betrayal.
- Zarosian Empire goes to war with the Kharidian empire. Icthlarin brings the Mahjarrat to Gielinor, and their deployment successfully defends the Kharidian Empire and drives out the Zarosian armies, winning the Kharidian-Zarosian War for the Menaphite Pantheon.
- Amascut's mind becomes warped and she becomes known as the Goddess of Destruction after witnessing the Mahjarrat and the destruction they caused.
- The Saradominist kingdom Hallowland with its capital Hallowvale is established in the modern Morytania region.
- The Mahjarrat abandon Icthlarin and become the followers of Zaros, making his already considerable military all but unstoppable.
- Gods and by extension their empires make a pact that if any of their empires are attacked by the Zarosian Empire then an alliance of Gods will declare war on Zaros. Unable to a defeat combined coalition of gods, Zarosian aggression is checked and a cold war begins amongst the various factions.
- Bandos learns of Gielinor and, sensing a war brewing, begins establishing colonies in territory not claimed by the other Gods.
- The Slayer Tower is built by General Viggora.
- The Zarosian Empire reaches its peak, consisting of Forinthry (today's Wilderness), northern Misthalin, northern Asgarnia and northern Morytania.
- Zamorak, a Zarosian general at the time, orchestrates his master's downfall.
- Zamorak becomes a god after Zaros' defeat.
- Zamorak travels to Infernus to assist the Avernic demons in overthrowing the Chthonians. It takes him and the Avernic demons 19 years to either destroy or exile the Chthonians. When he returns to Gielinor, he is backed by a vast army of demons, one so large that he could conquer the world. He declares war on the other gods, wanting to reclaim the Stone of Jas from Saradomin.
Regions controlled by known Gods by the end of the Second Age
- Guthix - during the Second Age, Guthix was sleeping and many other gods were active in Gielinor, so he had few followers.
- Zaros - the Wilderness (known as Forinthry during that time), Misthalin, northern Asgarnia, and northern Morytania were under his control. The Zarosian Empire was the by far the largest and mightiest by the end of the Age.
- Saradomin - Saradomin was much less influential in this age than he would later become. His strongest holdings were the mighty Hallowland, where his Icyene were garrisoned, and Entrana where, according to his monks, he first arrived in the world. He also had influence rivalling Zaros in areas like southern Asgarnia and the Kharidian Desert, primarily in cities like Uzer.
- Armadyl - assumed to be some parts of modern Kandarin, due to central Kandarin being the location of the Temple of Ikov and some other Armadylean sites. Armadyl had sole control of his various citadels in the sky at this time (these citadels are the Clan citadels used today).
- Seren - Tirannwn, and northern areas of Kandarin. Was mostly isolationist outside her territory.
- Menaphite Pantheon - both the northern and southern parts of the Kharidian Desert, though by the end of the Second Age, the northern Kharidian had became a cultural melting pot with both Zarosian and Saradominist worship widespread, especially in the cities.
- Bandos - Bandos came to Gielinor close to the end of the Second Age, near the beginning of the God Wars. He would begin to introduce various races such as Goblins, Ogres, etc. from Yu'biusk in preparation for war. His exact territories during this age are unknown.
- Fremennik/Barbarian Gods - Fremennik Province, northern Kandarin, as well as the Fremennik/Lunar Sea islands.
- Karamjan Gods - Karamja and possibly adjacent islands.
- Marimbo - Ape Atoll and the southern islands.
- Unknown - southern and western Asgarnia, eastern Kandarin, Southern and Eastern Sea islands.