Parasitic energy is the energy of accumulation, corrupted. Mashoaab is not easily corrupted, but when it is, it begins to steal energies from around it, becoming unstable very quickly. Wielding parasitic energy often requires combining it with methods of theft or taking:

Hematophagy - drinking blood to gain new powers
Souldraining - taking souls through parasitic energy to gain new powers
Heartdraining - taking emotional resonance through parasitic energy to gain new powers
Rune-Binding - bonding to another being in order to take their attributes - rune-smith
Minddraining - taking psionic energy through parasitic energy to gain new powers

A Defalcator is a user of this energy for criminal activities.