Revelations from Patch 4.5

[CaesarCV]

None of these are spoilers, so I'm not going to bother with the boxes.

The Flood of Darkness on the 13th Shard influenced the Source by introducing Voidsent to the realm. Which has created issues for mages in general. Those creatures love to feast on Aether and our world has plenty of Aether to go around. Given the differences between a Dark Void (Life, but no Aether) and a Light Void (Aether, but no Life), it's quite probably a Flood of Light would have some kind of effect on the Source. Only since that wouldn't be the introduction of some new kind of life, it would probably be the introduction of some kind of aether.

There's been some misinformation in this thread on a few points that I might want to clarify. First off, Igeorythm did not introduce the voidsent to the shard. What she did was introduce some sort of substance similar to Auracite that caused a horrific succession of wars and the like that eventually lead to the dangerous imbalance of dark and light that caused the flood. The mystical substance caused people to gain great power, but also slowly change and mutate into strange monsters. Voidsent such as Cu Chullain are said to have been former grand heroes who are but mutated mockeries of their former selves. The Voidsent that inhabit the former shard now known as the void were originally its mortal inhabitants. Over time through a mixture of this strange substance and some other factors they were mutated into the aether hungry creatures that now plague the source and (quite possibly) other realms.

Additionally, if I remember correctly the plan for Arbert was most definitely not to cause a Flood of Light or Darkness on the Prime. That would probably mean the destruction of all worlds. Their goal was to either try and mess with the balance through the Shard to reduce the Light on their home shard, or, failing that, cause a rejoining. Compared to the absolute lack of existence that would come with a Flood of Light, having their shard absorbed into the prime and the aether brought to the Lifestream seemed a better alternative. Granted, they were manipulated by Elidibus into going through with this plan, so it is very likely they were misled or wrong about certain aspects. Indeed, the closes thing to salvation for their shard came not through their brute force methods, but through a hopeful appeal to Hydelyn who sacrificed her avatar to try and protect the First Shard. Granted...that might not be working out too hot...

[Iscah]

Additionally, if I remember correctly the plan for Arbert was most definitely not to cause a Flood of Light or Darkness on the Prime. That would probably mean the destruction of all worlds. Their goal was to either try and mess with the balance through the Shard to reduce the Light on their home shard, or, failing that, cause a rejoining.

They were directly trying to force a Calamity (and thus a Rejoining of the First before it could be completely Flooded and left in limbo) by killing primals to drive the beast tribes to despair, so they would call on ever greater gods - presumably while the Ascians organise to conveniently supply the tribes with more crystals. Possibly they were doing other things as well, but that's what we see them doing.