I've been developing insect-looking bipeds that have evolved on a mostly jungle/ocean planet in addition to small, scattered grasslands. This is justified (from what I've read) by a thick nitrogen/oxygen/carbon-dioxide and humid atmosphere, significant amounts of water, continents mostly placed near the equator, and possibly a slower planetary rotation/adjusted tilt. These creatures are mostly predatory, developing and embracing an elite warrior culture and are likely the best soldiers and warriors in the galaxy, almost always outmatching any other galactic creature or society in combat. These creatures on average are around 7.5 ft tall and weigh roughly 200+ pounds, but these measurements are flexible to change if necessary.
Various fantasy settings depict humanoid-like and other non-humanoid creatures possessing the ability to generate and accurately direct lightning (Vortigaunts from the Half-Life series and Pokemon being the first that comes to mind). This ability is usually depicted capable of incapacitating/severely injuring other creatures over a moderate distance on land, usually over a couple of meters. The process by which the creatures in these settings generate and direct lighting is almost always hand-waved or just explained with magic/magic-like means. I envision my creatures possessing this ability, emitting lightning/electric shocks on land through tentacle-like structures.
Although there are creatures of Earth that are capable of bioelectrogenesis, these creatures are mostly fish like the electric eel. Although the electric eel is capable of generating electric shocks powerful enough to stun prey, their ability to produce electricity is nothing compared to that of the fantasy creatures described previously.
Is it biologically possible for these terrestrial creatures to generate and accurately direct lighting or electric shocks that can be used at a distance on land that is powerful enough to kill opponents or prey? If so, how energy demanding would such a trait be per shock for these creatures?