Arcane Singularities are highly energetic and highly unstable explosives. The slightest jar will cause it to explode. The explosions rips open a tear in the fabric of reality which draws in anything nearby and annihilating it.
Triggering an Arcane Singularity has an..., um, interesting effect on the local Aura.
Arcane Bore Edit
It can also be used in Arcane Bores, if you get an Arcane Bore and start it and then throw an Arcane Singularity in its mining range (Do not throw too close to the Arcane Bore) then nearly all the blocks it is supposed to annihilate gets sucked in the arcane bore.