Cloud of Tatra
The Cloud of Tatra is the largest nebula known in any universe, at 2800 light-years across. It is not within a galaxy or galaxy system, but floats freely in space.
Its size is possible due to how young it is. It seems the gas and dust forming it was removed from a nearby galaxy and accelerated away by events near the time of or during The Merge. Giant stars are constantly forming and dying within it.
Tatric Alliance members: