I think it's hard to do much with just HP or Nora cost here, especially in FW which has a number of playable low cost options. Lower HP would help but would still either eat a bunch of AP (at least 3 probably, more likely 6 or 9) or require an AE non-champion to be drawn. The only thing I can think of is that it triggers on a different condition - such as when it enters a font deployment zone, or if it was deployed at a font.
Actually I rather like the sound of that: triggering when the opponent deploys at a font. Would it still be costed at 30 nora and drop 3 Shades then, similar to Wake the Dead?
@Sokolov for black ops how about. The next 3 Liches you deploy permanently gain Eternal Life and costs 10 nora less.