I tried adding

function DepleteArchmage(item)
if item.being.theSpellCast.itemID == "Explosion" then
item.Deplete();
end
end

To a Lua file Artifacts.lua in my own mod's files. However when I try to add it with

<App trigger="OnSpellCast" effect="DepleteArchmage"></App>

on an artifact it causes an error when clicking Install Mods saying 'DepleteArchmage' doesn't exist.