Upgrading Drow hideout

[HoboKnight]

So,
I have this Drow caster (Archmage Stats) who fled Underdark. Guy had it with all the murders and poisoning and intrigues and he just fled Underdark when powerful enough. As per his regular modus operandi, he has a Clone precast, as well as 5 Simulacri of him rolling along just in case he needs some additional arcane firepower. Also he is in possession of Acorn of Dominance - he can permanently dominate any Awakened Tree. At this point he found a place in High Forest. He found a trio of Hags, operating in an abandoned castle nearby and Hags made a pact with him - he is the designated Storage guy for cursed items that Hags regularly produce. On the other hand, hags are a good connection to the rest of the world for him as well as a good front. Now. Guy is here for a few months and he moved into an old Druid cave in a forest near the castle as well has dominated a few Awakened trees.

What upgrades make sense for a Drow Mage to make to this place during several months? How would he store cursed magical items? What defenses would he apply?

I was thinking he could use Conjure X summoning spells, along with Magic Circle and Planar Binding. This would enable him to slowly accumulate a completely loyal army and perhaps some monsters that enable him to reshape what is, admittedly, a large, but empty underground cave with a single exit.

My masterful rendition here: https://ibb.co/Rv5s0Sr

Thanks!

[JackPhoenix]

Depending on resources (both monetary, spell knowledge and creatures available) and how much the archmage prefers convenience over security, here are few ideas.
Mirage Arcane makes finding the hideout at all harder. It has long enough duration that it doesn't really eat into daily slots, and the drow can change terrain around every few days. Good luck finding the entrance when it's at the bottom of a (semi-illusionary) swamp!
Also, consider if the drow needs to keep physical entrance at all. Dimension Door allow him to enter the hideout even if the entrance is sealed. It eats slot, but if the drow doesn't need to leave and enter too often, he can bring his hag allies along if he wants to.
Wall of Stone allows to redecorate the interior as he sees fit (or allows for sealing the entrance, as per above). Even if he normally keeps the entrance open, it can be used to "close the door" when an attack is imminent. It can also serve to secure the cursed: dig a hole, drop the artifact inside, cover the hole with stone, use Stone Shape or Disintegrate if you want it back.
The trees are decent, but you can go further: Planar Binding doesn't require the target to actually be extraplanar, just to have a specific creature type. Enslaving a bunch of unicorns, dryads and other fey that could reasonably live in the location (I'm sure the hags would gladly help to provide the workforce) to confuse and deter anyone poking around (Go away, this is normal fey grove, nothing to see here!), especially if the intruders are good-aligned.
Magma mephits make for a surprisingly useful guards if the intruders wear heavy armor. They are weak in combat at that level, but they don't have to fight, just poke out of a hole too small for medium creatures, cast Heat Metal and hide again to deliver 20d8 fire damage with no save and a disadvantage on attack rolls and ability check while the spell lasts. With no save.
Babau demons have bunch of useful spells (including at-will Heat Metal and Dispel Magic) and are tougher than the mephits, but they'll have harder time escaping retribution, and they are demons, so they may not be the most reliable "allies", even when bound.
Have a room packed full of skeletons and/or zombies. There's no need to control them, they'll attack anything that come close anyway (the drow would, of course, have ways to avoid their notice). They won't be very effective, but they can serve to waste the intruders' resources or time. Even a squad of paladins won't cut their way through a hundred zombies quickly.
Antipathy, Forbiddance or Hallow used inside can make for great defenses. The later two aren't on a wizard's list, but can be cast through Wish, if possible (and Hallow is better cast that way anyway). Also, funny thing about both of the later two spells is that while they can't be overlapped, their area CAN be adjusted. While it's unrealistic to have the entire playe filled with 5' radius-sized Hallowed areas, good luck getting through that Guards and Wards can be used too, but it's got shorter duration, so it may not be worth casting if the drow isn't aware of incoming threat.
As many Glyphs of Warding as you can get. Not just blasting, glyphs of Counterspell or Dispel Magic is a good measure against spellcasting intruders, Magic Missile has relatively low damage, but force damage with no attack roll or save is always nice, and summoning temporary reinforcements is always useful.
Of course, the REAL hideout is in a secure Demiplane. Good luck with that.

[HoboKnight]

Jack, why are you so good? :D Amazing and thank you!