Let me illustrate (only for destruction, maybe applicable to demo too):
1) You start off with a Succubus.
2) You seduce a target and burst him down.
3) You seduce a 2nd time, and burst him more.
4) You seduce a final 3rd time, and due more damage.
5) You use Sacrificial Pact on your Succubus.
6) You use Grimoire of Sacrifice to sacrifice your Succubus.
7) Enemy CCs you, you use Unbound Will.
8) You load up Dark Misery.
9) You shadowfury on him and begin nuking.
10) You now have +30% crit chance and +30% dmg and 2% HP per 5 sec regen for 15 secs, with a 200000HP undispellable shield. Do whatever you want with this, go nuking. You are essentially an Arcane Powered mage, with Hunter Spirit Bond, 5 Power Word: Shields, and +30% crit.
11) You instant resummon pet later if needed.