AP
? ... Hmm, idk ... Without any additional items, runes, or masteries, that's 118 bonus magic damage. If we just add
(312 Total AP after Passive) that's approaching 150 bonus damage on top of however much spell damage you're already doing. There is a slightly unclear description here. It applies up to 4 targets on hit, but does that mean that it will apply to the 4 nearest targets to the primary target, say for a single target ability, or only up to 4 of the targets damaged by an AOE ability? Either way you're talking about adding up to a total of just shy of 600 bonus magic damage to a single spell. If the latter is true, then it would at least limit some of the usability.
Another question. The words "spell" and "ability" have sometimes been known to be used interchangeably. Does this additional damage only apply to abilities that apply spell effects, or does it also apply to on-hit abilities as well.
DFG at least required an activation (which some people either didn't use, or weren't good at using at the proper time) AND the need to have a follow up spell, or many follow up spells that would shred the single target. I fear that this item will make ANY spell into a burst spell, even if it doesn't already do a whole lot of damage to begin with.
Is this official, speculation, or suggestion?
Either way, I don't mean to seem too critical. I doubt that I would be able to come up with a perfectly balanced item myself If it makes it's way into the game I'm sure that it would find it's place, or be swiftly put there by All Knowing Riot.