Activate the skill to place the charge, then retreat to a safe distance, and activate the skill again to start the detonation - a fast burning gunpowder-like trail will rapidly snake back to the place the charge was placed, and then ignite.
The path of the 'gunpowder trail' will damage enemies. The trail will follow whatever path was traversed from after setting the charge down till detonating it.
The 'gunpowder trail' not only inflicts minor damage but has a strong Stagger or Knockdown effect.
There is a limit to the total distance the trail can burn - approximately equal to a shortbow's effective range - if this length is exceeded, the initial charge will not detonate, but the trail will fizzle out prematurely.
The main blast damage is predominately related to Strength. If an enchanted weapon is equipped when the skill is used, Magick power is also factored in.
It is likely that the behaviour with Enchanted weapons is similar to other skills (like Flameshroud) - that is the physical damage is related to total attack strength, but the magick damage only scales with the magick attack of the weapon held itself.
With a typical enchanted weapon damage scales approximately in the ratio 7:3 - physical to magick (with periapts)
The damage from the trail and blast does not affect the Arisen or allies.