I am running a game with 7 PCs, level 13. PCs are all different classes and have an array of magic items and bonus feats and/or spells. I am planning on having them face Orcus with about 3 of the PC's personal nemesis (mini-bosses, +2 weapons and legendary actions) 4v7, overkill?
If you do decide to run the “Official” Orcus as per Mordenkainen’s Monsters of the Multiverse, be aware it really only has 1 gimmick but that gimmick is pretty nuclear. Orcus will immediately start things off with summoning some combination of Lich variants (up to 500 HP) including: a Dracolich, a regular default Lich (lame), a Mind Flayer Lich (better), an Eldrich Lich (Spelljammer Compendium), and/or a Lichen Lich. Or, and this is technically allowed, he summons a single Dracolich … and Vecna the Archlich. The Wand does not limit itself to non-unique or named creatures. After that, Orcus is himself pretty lame, just a lumbering bruiser, and not particularly dangerous at all at 13th level. With clever use of spells and positioning I feel a 13th level party could take him, but I’m unsure about him and Vecna together. Pack in these 3 other mini bosses of yours - who should come in with good movement and maneuverability options (flying, teleporting, burrowing, whatever) as well as senses (devils sight, tremor sense, blind sight, true sight - and it’s probably a TPK. More info and I can better help out always.
Edit: As a note, I highly recommend homebrewing your own Orcus, if it’s actually Orcus you mean for them to fight. Orcus is a Demon Prince that Rules multiple layers of the Abyss, which means he bosses around mobs of Balors and Molydei. Assuming you aren’t a person who would argue he’s a nigh divine cosmic entity (easy argument to win though) I can’t see this creature being any less than a CR 30 with Legendary and Mythic status (or some variant of, basically phase fighting where various health thresholds create new actions), and almost certain with a Lair.
I am running a game with 7 PCs, level 13. PCs are all different classes and have an array of magic items and bonus feats and/or spells. I am planning on having them face Orcus with about 3 of the PC's personal nemesis (mini-bosses, +2 weapons and legendary actions) 4v7, overkill?
If you do decide to run the “Official” Orcus as per Mordenkainen’s Monsters of the Multiverse, be aware it really only has 1 gimmick but that gimmick is pretty nuclear. Orcus will immediately start things off with summoning some combination of Lich variants (up to 500 HP) including: a Dracolich, a regular default Lich (lame), a Mind Flayer Lich (better), an Eldrich Lich (Spelljammer Compendium), and/or a Lichen Lich. Or, and this is technically allowed, he summons a single Dracolich … and Vecna the Archlich. The Wand does not limit itself to non-unique or named creatures. After that, Orcus is himself pretty lame, just a lumbering bruiser, and not particularly dangerous at all at 13th level. With clever use of spells and positioning I feel a 13th level party could take him, but I’m unsure about him and Vecna together. Pack in these 3 other mini bosses of yours - who should come in with good movement and maneuverability options (flying, teleporting, burrowing, whatever) as well as senses (devils sight, tremor sense, blind sight, true sight - and it’s probably a TPK. More info and I can better help out always.
Edit: As a note, I highly recommend homebrewing your own Orcus, if it’s actually Orcus you mean for them to fight. Orcus is a Demon Prince that Rules multiple layers of the Abyss, which means he bosses around mobs of Balors and Molydei. Assuming you aren’t a person who would argue he’s a nigh divine cosmic entity (easy argument to win though) I can’t see this creature being any less than a CR 30 with Legendary and Mythic status (or some variant of, basically phase fighting where various health thresholds create new actions), and almost certain with a Lair.