Dare I mention hypercomplex numbers? The first ones you come across are quaternions, represented by set H. Something I learned a few years ago, in set C there

Dare I mention hypercomplex numbers? The first ones you come across are quaternions, represented by set H. Something I learned a few years ago, in set C there are two solutions to x^2+1=0, but in set H the set of solutions forms a Lie group, or basically an infinite number of solutions.