Help me find a spell

[Thac0 Redeye]

I am looking for some type of barrier spell. I think force wall is too easily dispelled. I need it to be either impossible to bring down or very hard. The party has a warlock and he just zaps all the locked doors to get through so I can't just put a master level lock on it. the room would protect the necromancers workshop and I don't think the party is ready for it. When he zaps the door I would like them to see a opaque magical barrier.
Or perhaps is there a way an 11th level dread necromancer can cast a hard to dispel force wall? items? any ideas?
thanks

[Zaq]

Easily dispelled? Wall of Force? Are we reading the same spell? Wall of Force is explicitly immune to Dispel Magic. It takes Disintegrate or Disjunction to get through a traditional Wall of Force. Just what is that Warlock packing?

[BlackOnyx]

When he zaps the door I would like them to see a opaque magical barrier.

While not all of these would necessarily create an "opaque wall," if your Dread Necro has access to UMD and scrolls, you may be interested in spells like:

Forbiddance (permanent)
Phase Door (permanent until used, 1 use/2lvls)

or, if you can permanency certain spells:

Hand of Torm (can be attributed to appropriate deity)
Forcecage
Wall of Force

Illusory Wall (permanent) and Permanent Image (permanent) might also be useful if you wish to hide the entrance entirely.

Door of Decay is also explicitly listed as an option for the Dread Necromancer's advanced learning ability and could be used to negate the need for a physical doorway altogether.

[Fizban]

Greater Sign of Sealing has a higher dispel check than normal and seals open spaces with force, while Phase Door can only be used by those designated when the spell is cast. Portals can only be used however you decide they can be used.

If you want the BBEG to be bootstrapping their fortress personally, then Dread Necromancer is not a class that can do that.

And yeah, "when the warlock zaps the door" doesn't mean anything. Dispel Magic doesn't work on Wall of Force, Eldritch Blast isn't any better at smashing through doors than a big axe, etc. Specific answers require details.

[Thac0 Redeye]

ok so I should have re-read the spell wall of force before I posted. I think that will work. I was under false remembrance that it was subject to dispel magic.

as for the other questions, the warlock zaps the standard door and I wanted the barrier behind the door as a "lock" for when the necromancer is creating new undead.

so thanks everyone.