ScriptEffectStart
Usage
begin ScriptEffectStart
Special block type used only by Magic Effect scripts. This block will run on the first iteration of a scripted spell effect.
The fact that Script Effect Spells run on whoever has been hit by the spell, basically gives the programmer the ability to apply a script on any Actor in the game for a period of time, and can be used for getting Actor reference and many other effects. But keep in mind that spells will only work on actors, containers, or doors; the last two being for unlock spells. Dead actors also work, but the update block only runs for a few frames.
Note: When a scripted effect is used as a weapon enchantment effect, the effect will take place AFTER the weapon hits (ie. The weapon damage will occur before the scripted effect). This means that the scripted effect can be used for soul trap like effects that need to occur after death.
Constant Enchantments
Unfortunately, this block won't fire when used as a scripted effect for constant (apparel) enchantments. If you have access to the item script, you can emulate the functionality by using the OnEquip block of the item itself.