globe of invulnerability ends, and I fly out of your range again (to 160 feet up). (I know that you still have feeblemind, I'm not going to fall for that one)

oops, I can't disintegrate and be out of feeblemind, so I cast lightning bolt instead. (roll dex or take 21 lightning)

Quote from iExist >>

spell ressistance from what?

 Spell Resistance from the Abjuration subclass (literally just called Spell Resistance).

Dex save: 18

I take 6 lightning damage (Arcane Ward is on 27 HP).

I use my free casting of Fireball on you (the blast radius thing again). 5 1 3 5 1 6 2 6

(I don't know how to view the individual dice rollls on this thing so I'm just going to do it this way.)

(I just worked out how to do it, but I've already rolled these so I'll go with it.)

 Those 1s count as 2s (fire adept) so 28 fire damage.

okay.

I drop 40 feet down, bonus action convert a 2nd level slot to sorcerery points, then I cast heightened wall of stone. roll a dex save (no advantage or disadvantage because heighten) or be trapped inside (yes, I included a roof)

Very well. Dex save: 18

Well that's vaguely frustrating.

Sorry I missed the no advantage bit - I failed anyway though so it doesn't really matter.

I wait it out, casting Shield every turn (with Spell Mastery) to bring my Arcane Ward back up to full HP.

When I'm done with that, I take a Short Rest using my Arcane Recovery to regain my 1st and 3rd level spell slots and regain my Signature Spells.

I then take a Long Rest because why not? I would argue that busting your way through a stone wall that would then fall to the floor would make enough noise to wake me up.

If I make it through the entire Long Rest, I replace Blur with Forcecage on my prepared spells list.

I'm running considerably lower on resources than you are. why would I NOT long rest when I get the chance? spell slots back, and all my sorcerery points too.

also, you can't cast shield a bunch to do that, I'm not attacking you and that's the only condition that shield can trigger in, other than magic missile

oh yeah, before you can do all that stuff, I'm going to use my remaining 5th level slots to triple-layer the prison

if you want out of there, feel free to waste a few slots on it. it will make this battle much easier for me.

Quote from iExist >>

also, you can't cast shield a bunch to do that, I'm not attacking you and that's the only condition that shield can trigger in, other than magic missile

 Shame. It doesn't matter anway - When I wake up I take the liberty of casting Mage Armour on myself to activate my Arcane Ward (and get an AC boost).

I'll make a start on breaking out of the prison thing - using Scorching Ray so I don't waste any spell slots.

I won't bother rolling for attacks, I'd eventually break free anyway. I stop when the final section of panelling is on shall we say 14 HP.

To let you get ready and for me to prepare too.

as soon as I see the wall starting to crumble, I cast globe of invulnerability and fly up to 30 feet above the roof. (because globe of invulnerability is awesome)

edit: actually, I just ready an action to do that when you appear

Sure. I assume that you moved beforehand because you can't move away and cast at the same time with Ready?

I cast Longstrider on myself, then cast Scorching Ray on the panel - for the sake of simplicity I'm not going to bother rolling. If, somehow, it failed to destroy it I'd just have done it again next turn.

P.S. Globe of Invulnerability doesn't protect against, say, a 6th level Counterspell - the description doesn't specify base spell level, just spell level. In the Player's Handbook it says that "if Umara casts magic missile using one of her 2nd-level spell slots, that magic missile is 2nd level." so I could cast a Fireball of high enough level and it would have an effect.