A lot of people are saying that orbs are made of light, its obvious. Light. In the shape of an orb. Fair enough. But I think it bears further examination. Guardians have a super ability that is the most common source for creating orbs. Some gear also adds the ability to create an orb of light from a certain action. Some supers are activated and automatically create orbs of light, such as a Titan bubble that creates two orbs. I would guess that on this situation, there is a certain amount of power that activates the bubble, and the two orbs are kind of "leftovers" and can be collected by other guardians. So perhaps its a situation that to activate the super ability takes a certain amount of this power, but once its activated, excess ambient energy manifests as an orb. Other supers, such as bladedancer, activate but don't create orbs until the user gets a kill. You may think then, that there are two different types of orbs; orbs from super power, and orbs from kills. Super energy builds within a guardian at a speed dictated by their intellect. But the pace at which super energy is generated accelerates from killing enemies. Gear that grants orb creation capability usually manifests with "Kills of this type have the chance to generate an orb." Or "This certain type of damage has the chance to generate an orb." So when we put it all together, orbs are "light." Light that builds up within a guardian over time, but everything that helps to accelerate that process is death. Death of enemies. Perhaps because guardians are ressurected, the state of death that they perpetually exist in, creates super power through the mechanism of their undead existence. So the previois assumption that some supers generate orbs from killing and some don't, can be rendered moot when we take onto account that the light is generated within an undead being, and when that being kills, more light is generated. So the titan bubble that drops two orbs may not be actively killing in that moment, but it was death and killing that powered the ability to create the orbs and the bubble in the first place. So in summation, light is a tangible manifestation of the death that a guardian has caused. Causing more death generates more power. Perhaps it is the life that was taken from the killed enemies, trapped in an orb. Perhaps in super mode, the guardian is expending so much light that it cannot absorb any light. When in super mode, kills generally do not give the user more super energy, perhaps because in super mode they cannot absorb it, since they are exuding so much power, so the light enters the guardian, is unable to be retained, and gets processed into an orb which then ejects from that guardian as an orb. Basically, in super mode, you are expending power and it gets used and ejected from a guardian's body, usually in a way that the guardian has learned to channel, such as in the use of a super ability. The excess, instead of getting absorbed, gets ejected. Of course, some super ability nodes include the skill of increasing the duration of a super ability's duration when getting a kill. Again, this re-enforces the notion that death itself is the catalyst for light. Perhaps when guardians roam the planets, they are building their super energy meter through the absorption of the ambient life in the area, and killing gives a boost to that super energy meter. This would explain why guardians are not allowed in the city among normal humans. It's possible that the mere presence of guardians would absorb life from the area and corrupt the city's resources. Humans appear in the tower, so its likely that the life absorption would not be sufficient to harm living beings on that level, added evidence to that would be the fact that the fallen do not die or take damage from the mere prolonged presence of a guardian. There is the old saying "The light at the end of the tunnel." Used to describe what people see when they die. Based on my previous conjecture, I submit that orbs are created from death, and the light guardians use for power is the same light at the end of the tunnel, so to speak. It is the light of death.

Considering that they're called orbs of light I feel like the most obvious and logical answer is that they're made of cheese.

1's and 0's

They're called "Orbs of Light"... How have some of you people survived this long? Geez

i remember the good noob days how the -blam!- do i make orbs