Empathic Obliterator

The Empathic Obliterator is a unique Necron staff carried only by the Necron Overlord Trazyn the Infinite. This terrible weapon is rightly feared by the enemies of Trazyn, and there is a dark rumour that the staff contains technology derived from that of the long extinct Old Ones. When an enemy is slain by the staff, a psionic shockwave bursts forth from his body, potentially killing nearby creatures of a similar mind and purpose.

Hence, an entire squad can be wiped out with a single blow of this horrific weapon. The Empathic Obliterator suits the personal combat style of Trazyn as he disdains physical combat with "inferior" beings of flesh and blood.

Sources

Codex: Necrons (5th Edition), pp. 27, 59