I'll repost this here. This is from a thread I made to try to get some Morde discussion. Looking back at it, the idea needs work. It would be better to find a way to bring the price to 3,300 and the AP to 120, like your suggestion. However, I do like the idea of keeping DFG in some form or another, afterall, DFG even has its own song from the Pentakill band. I might take another look at it when I get home today:
Deathfire Grasp
3700 Gold (Needlessly Large Rod + Twin Shadows + 100g) [With this change, Twin Shadows loses 20 AP and has its price readjusted to 2,000g.]
140 AP [Keep in mind that Rabadon's provides 156 AP on its own, grants an added 30% of all other AP sources, and is cheaper than this new DFG]
10% CDR
6% MS
UNIQUE Active - Hunt: Summons up to 2 invulnerable ghosts that seek out the 2 nearest enemy champions for 6 seconds. If a ghost reaches its target, it reveals the target while reducing their Movement Speed by 40% and transferring 15% of their AP to the caster for 3.5 seconds.
If a ghost cannot find a target, it tries to return to the caster. Ghosts that successfully return in this way reduce the item's cooldown by 40 seconds (120 second cooldown).
[The 15% transferred AP could be swapped out for just a 15% MR reduction, which would be more similar to current DFG's effect while still pushing the item to later game and still making it somewhat less bursty.]
With the above addition, DFG would be shifted to a lategame upgrade (price on par with Triforce and Infinity Edge) in stead of an end-of-laning purchase. DFG would go from being the cheapest Needlessly Large Rod upgrade to the most expensive. Champs like Mordekaiser would still want it but would be less inclined to rush it, leaving them less bursty mid-game but helping them have a lategame fantasy. The new item would offer less instantaneous burst potential (%health active damage is out of the equation) while perhaps giving champs like Morde some chance to actually catch opponents (it would still be very difficult). In a straightforward teamfight, the ghosts would also be most likely to strike the enemy front-line, granting the active effect some counterplay, whereas the user would really want to hit the enemy APC with it. The addition of this new item would also have the benefit of encouraging people to actually use Twin Shadows, which has a really cool effect despite the community's general neglect of it. All in all, this would be a great item for mages' duels.
I do think that the change of item identity is fitting with the title "Deathfire Grasp," which calls to mind a vision of one's victim being clutched by the souls of the damned and dragged into the infernal depths of hell (ie., Morde's foreshadowed onslaught).