I started working on- but never completed- an alternative version of Energy Drain:
It would be a 4 step condition degradation. Energy Drain attacks would work by making a PC Fatigued => Exhausted => Staggered => Unconscious. Energy Drain could not kill directly, but could render a character vulnerable to a coup de grace
To clarify- this shouldn't happen on 4 consecutive hits. That would be too much, too fast. It needs to be conditional.
1) Perhaps it takes a crit to bestow the condition- and more powerful Energy Draining undead have better odds of scoring a crit.
2) perhaps an Energy Drain attack only succeeds at draining energy after a failed saving throw.
3) it could be something that requires the undead to expend a resource of its own, like burning one of its "4/day" or "4/Encounter" Drains; etc.
4) perhaps- for certain undead- it could be contiditonal, so that they could Drain only on unholy ground, under a full moon, etc.
5) for truly anathematic creatures whose very existence is an affront to life (major undead, powerful aberrations, certain extraplanar beings), they might even Drain in a continuous aura, and the longer you stay in the aura's radius, the more you are drained (IOW, you must save each round, and if you fail, your condition worsens). Such an aura may even do some HP damage in addition. For such creatures, I would say that either you only need save once, regardless of the number of overlapping auras you encounter, or this kind of aura is limited to unique beings, just for mechanical reasons.
6) it could be a specialized die-roll mechanic: for each event for which an undead could Drain a foe- either by attack or by aura- the DM would roll a special die (let's say it's a d10). Weaker draining undead only actually Drain on a 10, but more powerful ones might drain on a 9, 8, 7, or even a 6.
Overall, this system has 4 main advantages I can see: it would use existing game mechanics without really creating much in the way of new substystems, just a new way to use them; the mechanics match the fluff; the danger is real (for any class); the bookkeeping is minimal.
The main disadvantage is that I’d need to rework spells & items that drain energy, and there’s quite a few of those. That difficulty was the main reason I didn’t finalize this design.
