Ah, against the Sorcerer level 11?
Open a gate? Please, It will be fun. Get popcorn to watch them defeat you.
This is the one I am interested in. Here is how I see it.
If we have the 20th level wizard use the gate trick against an 11th level sorc, the Wizard is going to have at minimum a 7th level globe of invulnerability on as a buff, and probably several strong warriors ready to pounce (which the globe will protect unless the warriors move. There will probably be other things (mind blank is one strong possibility). But lets go with the basics.
The wizard has a few options:
1) Anti-magic field: The simplest option would be to cast anti-magic field and move in on the sorc. The sorc and wizard become schleps, and the warriors beat the crap out of the sorc. Without magic and allies, the sorc has no chance.
The issue with this is the Wizard has to trust his warriors not to turn on them in its weakened state, and a world seeking wizard might be too paranoid for that.
2) Simulacrum double cast. One of the sorcs greatest weapons in this fight is counterspell. While his counterspells are not as strong as the wizard, many people (myself included) rule that subtle spell negates counterspell, which is a major advantage to the sorc. One way the wizard can beat that is with simualcrum (just 1, again no cheese). Both wizards cast, and at best the sorc counters one of the spells, and is fried by the other.
Since wish makes it free, it would be absurd to assume a wizard without a simulacrum
3) Power Word Kill: I've noted before that its extremely unlikely that an 11th level sorc will have more than 100 hitpoints. So power word kill is one way to just end the fight right off (assuming the simulacrum has it). The sorcs main counter is counterspell, which assuming a +5 cha (a reasonable assumption for such an 11th level character) would have a 35% chance of negating the spell. Poor odds for the sorc, but not exactly the auto kill we were hoping for. Now if we go with the simulacrum double cast....than it comes down to the DMs interpretation of counterspell (aka do they use the Xanathar's ruling which means they would basically have to guess on which spell to counterspell). And even if they know its still a rock in a hard place. They might dispel the power word kill but the main wizard could still unload an extremely nasty other spell.
4) Planar Bindings: A wizard can use wish to summon an 8th level planar binding, which has no components and lasts 180 days. In theory the wizard could have have dozens of these creatures in his lair ready to destroy whoever comes through the gate, if normal men are just not sexy enough for you.
5) Feeblemind: A wizard can cast feeblemind at a nice safe distance out of counterspell range. Its an int save, so a very low chance of success for the sorc. The only way to fix it are spells the sorc does not have access to. This is a lesser power word kill, it doesn't kill the sorc, but it neuters them to irrelevance, for the wizard to then kill at its leisure.
6) Spell Mastery attrition fight: So another option is for the wizard to just spam its spell mastered spell. Sure the sorc has a lot of spell slots, but they aren't infinite. The sorc can counterspell but only for so long. As long as the globe is up, eventually the sorc will fail.
So those are just a few ways the wizard could take out the sorc. Is there anything the sorc can do to counter?
1) Dispel the Globe. Again if we assume subtle spell blocks counterspell, the sorc could attempt to dispel the globe. The standard 3rd level which is a 50/50 to dispel, not amazing odds but there's a chance.
Once the globe is down than it comes down to straight spellcasting. Now in a straight up duel 1 on 1, I think the sorc has a chance. Better counterspells, heighten and quicken spell. The wizard has stronger spells and better save dcs, and of course wish can deal with a LOT of things. The sorc is definitely behind, but if the dice gods are kind than I think its a possibility.
The math changes completely if we assume warriors with the wizard. If the wizard moves in on the sorc with this warrior army, the sorc can't effect them with spells (globe), and will start taking a lot of damage (which also has a high chance of knocking down concentration, which likely would free the wizard from the majority of nasty effects). So assuming the sorc gets off that dispel, he is still under a ton of pressure. While there is a chance his spells could get through and stop the wizard (not kill him, but disable)....but doing that to the wizard and surviving the goon squad is too much to ask for.
2) Dimension Door. Especially if the sorc wins initiative, he could attempt a dimension door. Now that is quite risky as he is now in an unknown lair, but its an option. The main issue is that a locate creature can pick up even a sorc that uses an enlarged d door. Further, the sorc is in another plane, with no means of getting home. And lastly, the sorc has no means of blocking divinations and scrying. The wizard can find him, and then kill him.
3) Summon a creature. The sorc could summon a creature of their own, but against a wizard, his simulacrum, and a group of warriors, one summon is not going to do much. It could be dispelled or simply killed, and if that costs the sorc his concentration than he is even bigger trouble.
So ultimately if the wizard uses the gate trick, and has a modicum of sense and preparation, I can't fathom how a sorc manages to beat them.
