What can Orcus do with Time Stop?

Question

Last night I pitched the Demon Lord Orcus against my level 19 players. With a 26CR, I expected it to be a bigger challenge than it was. Orcus had a Wand of Orcus, and summoned a Nightcrawler, a Death Knight, and a Poltergeist against the 5 party members.

While holding the wand, Orcus can use an action to conjure undead creatures whose combined average hit points don't exceed 500.

Our Necromancer stole the Nightcrawler, our Monk stunned the DK for 3 rounds, and the Poltergeist got the wrong end of our Paladin's Holy Avenger. Anyway, as the fight starts, Orcus catches some of the players off-guard, and Time Stops in his first turn (no one was able to Counterspell it). But then... I had nothing to do during 5 turns. I moved Orcus closer to the enemies, and laid a Circle of Death, which ended Time-Stop. I'm not sure what Orcus should be doing when using Time Stop.

Initiative doesn't run during Time Stop, so I couldn't use lair actions to make more zombies.

Orcus causes up to six corpses within the lair to rise as skeletons, zombies, or ghouls. These undead obey his telepathic commands, which can reach anywhere in the lair.

All his undead-creating spells take 1 minute (Animate Dead, Create Undead). All his other spells or abilities affect creatures (aside from Detect Magic). Is Time Stop only useful to run away? Or to maybe force enemies to burn a higher-level counterspell? How can Orcus use his 1/day Time Stop spell offensively?

Answer 1

He can reposition

As the fight progresses, Orcus is likely to find that the heavily-armored tank characters are standing in front of him, and the lightly-armored ranged attackers are far away. Orcus can use time stop, then fly over to the more vulnerable targets, then make a normal melee attack.

He can shake off debuffs

Orcus has very good saves (and legendary resistance, and magic resistance), but if Orcus becomes affected by a debuff that allows a save at the end of each turn to negate, he can use the time stop turns to make saves.

For example, if someone casts sympathy on a five-foot area, Orcus might be forced to walk to that area and be unable to leave it. He can make a save at the end of each turn if "unable to see" the area, but for obvious reasons he doesn't want to have his eyes closed while in combat. Time stop solves this problem.

He can use dispel magic

Using this on a creature is likely to end the time stop, but using it on an area seems safe.

He can use the wand, if he hadn't already used it

While holding the wand, Orcus can use an action to conjure undead creatures whose combined average hit points don't exceed 500... Once this property of the wand is used, the property can't be used again until the next dawn.

This probably ends the time stop, so if the only thing Orcus wants to do is activate the wand, he might as well just use his action for that.

Answer 2

He can possibly cast Animate Dead with his Wand of Orcus

Using the wand only costs an action instead of the usual casting time. He can choose to cast it at level 9 each time (because stat block reasons) so could add an almost entirely worthless amount of skeletons or zombies to his 500hp horde... Yay go him.

However creating an undead creature could be counted as affecting a creature other than him, which would cause time to start again. I am not exactly sure how that works.

He can also dispel magical effects

Casting dispel magic on an area effect spell doesn't violate the Time Stop rules.