Borneo is a location in Among Thieves. It is the third largest island in the world and is located to the north of Australia, with a mostly jungle-filled landscape. While the northern side of the island is Malaysian, the rest of the island is Indonesian. Borneo also appears in Drake's Deception as a multiplayer map in co-op adventure.
In the 13th Century, Marco Polo was separated from his fleet of thirteen ships, which were shipwrecked on the island due to a tsunami. The ships were carried far inland, with the surviving crew managing to make it to safety in an ancient ruin on a hilltop. They never left the ruin after that, apparently killing each other en masse, indicated by the large number of skeletal remains, all of which bore blackened teeth, as well as bloodspatters visible under a light lit by resin from the Tree of Life.
After the events of "Breaking and Entering", Harry Flynn informed Zoran Lazarević about the location of Marco Polo's lost fleet, giving him and his men a three-month headstart to set up camp and search the Borneo jungle. Nathan Drake and Victor Sullivan arrived after the former was let out of prison, and discussed a plan to gain access to Lazarević's collected Polo journals with Chloe Frazer's assistance. Chloe had planted explosive charges in advance, leaving the detonator to Nate and Sully.
The two made their way through the jungle, eliminating several sentries and arming the explosive charges, until they managed to find Zoran's main camp. After starting the diversion by setting the charges, they raided the camp, discovering that the Cintamani Stone was never in Borneo at all, and that Zoran was instead looking for the true location of Shambhala. Nate further figured out that Polo's crew must have gone for higher ground when they got stranded.
After a long firefight with several groups of Lazarević's soldiers, Nate and Sully had made their way to the hilltop, rediscovering the ancient ruin and its grisly contents. They found a Phurba, as well as a map that would help them get closer to Shambhala. Upon trying to leave they were accosted by Flynn, although they managed to escape with the help of Chloe who served as a double agent.
In the non-canon mission Nate, Sully and Chloe infiltrate Lazarević's camp to discover what is in Draza's crates. After collecting the four pieces of the Janus Head, having killed Draza, they travel to London.
Borneo's jungle features a combination of a mountainous and swampy terrain, with thick plant foliage keeping most of it from being passable. At times the area features numerous small cliffs, with tiny canyons allowing for passage through and across. Water permeates most of the lower areas, although smaller streams can be found higher up. The only animal actually seen by Drake is a toucan, which is not actually native to the island nor the continental area.
Lazarević had at least two camps, and several more unseen dig sites. The main camp contained his personal cabin, and was located next to three shipwreck remains. A watchtower with a mounted gun turret oversaw the area, with unbeknownst to anyone a path behind it to the hidden ruins. The second camp consisted of a section on-top of a small cliff, accessible by a ladder, with a jeep, crates, and several tents. The section below the cliff had a series of wooden walkways to traverse the flooded terrain, as well as two desks beneath tent canopies at the other side. A large water pump was positioned between the two, with a big hose leading to the main camp.
The ruins on the mountain top, located next to a large cliff above a river to the sea, were in decline, with a gap in the floor leading to a lower level. Said lower level was almost entirely littered with skeletons and ancient dried bloodstains, that appeared blue under the light of burning resin. A section of tall stone statues ring the inner area, with one statue's head having fallen off. Polo's crew used one of the side rooms for storage, whereas the passage to the other was partially collapsed, although it did not contain anything of note pertaining to the ruins themselves.