Zectronic beam

A Zectronic Energy Beam was a powerful device that could conquer the universe 'in a matter of moments' according to the Doctor. When pressed about how this was to be achieved by his companion, he merely said 'I'll explain later'.

Zectronic Energy was capable of destroying the regenerative process of a Time Lord, but nonetheless the (Handsome) Twelfth Doctor regenerated into the (Female) Thirteenth Doctor. (DW. The Curse of Fatal Death)