Ya creating the event on your own would be easiest.
Here is what I would do to set up something like that.
It would all be quest based, I use Perl Express to edit and create most of my quests, can be found here...
http://www.perl-express.com/
** If you do not know commands and such for the emu, you can use GeorgeS tool found here
http://www.eqemulator.net/forums/showthread.php?t=22542
There is also a guide to writing quests, I couldn't find the link on the forums or in the wiki, so I uploaded it up to my personal webspace through my ISP, which can be found here...
http://members.cox.net/mithmarr/EQEmuQuestLexicon.pdf
as for setting up the event....
I would create an NPC and add it to the zone, the NPC would be the shadowman race (race 127) so you wont see him.
His quest upon spawn would spawn how ever many other mobs you wanted, you can even set the location of where you want them to spawn in the quest
** note ** From my experience you have to reset the server for the quests to take a hold, so do not expect for you to save the file and be able to use it the exact second afterwards without resetting, if anyone else knows how to do that maybe you can post and ask how. As far as I know you cant.
Examples...
this spawns the orc runner I made in Crushbone when retlon brenclog spawns.
Code:
sub EVENT_SPAWN
{
quest::spawn2(999171,23,0,-86,-395,6,0);
}
How that would work, is you would #dbspawn your created invisible NPC tied to that script, he would in turn spawn what ever you put in his quest code.
As for the henchmen thing you want...
create the henchmen, then when they spawn using the above code you can use the GM command to have them attack the player(s) of your choice using #attack [charname], that would make the targeted NPC attack that player.
Hope that helps.