FarBeyondC
Explorer
Seriously with 8 beholders, 1 red great wyrm, 4 solars and 5 storm giants. That is some ball-sy adventurers.
I suppose you could plane shift and then deal with the 4 solars who gave chase.
So, about that...
The fact that nothing on this list is immune to non-magical weapons means that something like my AL armorer/necromancer could handle everything that's not the adventuring party on this list through the use of spells and mundane items.
I'll leave off everything that probably wouldn't fly in this scenario and just stick with the necromancer herself and one day's notice.
Day 1: Make Simulacrum of self (long way), move client into created Demiplane for client's safety and Wish -> Hallow it, have Simulacrum of me True Polymorph itself into the wraith factory (aka an atropal), start wraith factory, get as many longbows, arrows, and suits of armor as possible for wraiths, have wraiths armed, armored, and commanded to kill anything and everything not me, the client, or the atropal, rest.
Day 2: Let something on the order of 800~7200 Wraiths annihilate everything else via Life Drain (everything not the solar) or arrows while the necromancer chills with the other party members wondering why they were even here.