*Delayed response*
A few ways:
1. use honor virtue
2. run very fast and pray
3. method #2, but with invisibility precast (or pots)
4. try again later, sometimes he wanders in to the entrance area (but not often)
5. bring a decoy (A friend is better than a pet)
6. stealth
7. fight your way in
I typically use method #3. People I go with use method #5 (I make a great decoy and it's the safest method unless I screw up). Once I used method #7, but that just made me rich and I never made it to the necromancer.
There's another one too... method #8: kill all the spawn until everything spawns either in the graveyard, the back corner or Red Death's stable. It gets you gold, items a chance at marties and thesis notes, then you can march right in, just avoiding Red Death.