Damages scales with magic, and can be boosted with periapts and potions.
Each monster damaged has a strong chance to heal the caster, as with all holy based offensive spells.
If cast with a debilitation inflicting weapon, such as an upgraded Rusted Staff it can inflict a debilitation (eg poison or torpor) on any foe that stays within its area of effect for a long enough time - in practices susceptible foes include skeletons and undead.
As an 'offensive' spell more useful to inflict debilitations than damage.
High Halidom is approximately 50% more powerful than Halidom.
The offensive power of the healing holy spells are similar though Halidom is slightly more powerful than Spellscreen or Anodyne
Halidom is nearly as powerful as High Anodyne, and whilst High Halidom is stronger it does not damage as often.
More than one sigil may be active at a time, though in practice it is difficult to incant two simulaneously.
Both forms have a similar radius of effect, around one bodylength
Although it will not cure general lowered attributes, it will cure curse.