Blue
Ravenous Bugblatter Beast of Traal
Our campaigns get to this level, but not usually too much further. So I'll talk more about the start of it from experience, and further up from theory.
Party synergy is more important than any character build. And a common issue I see when people build high level characters for one shots instead of characters that started at low levels and grew together is that they don't really have it. Coming in at 12th so many of your character choices have already been made. I would ask the DM to allow character tweaking for the first couple of sessions as you learn the other characters.
At these levels the party has a lot more in it's bag of tricks. Casting/ritual use of divination spells daily for instance. It should change how play flows to some degree.
For the DM, characters will have lots of high level spells. If they don't do enough encounters per day to run the casters down to a good amount of cantrip/low level offensive spell usage (vs. utility/defensive), then the long-rest recovery classes like pure casters will dominate the other classes.
At higher levels, common use of things like Simulacrum to double up casting, "microwaving" opponents (holding them in place and kill just standing there, such as forcecage plus heat metal or sickening radiance. And don't forget frequent conjured allies for meat shields and damage.
Multiclassing has more payoff - delaying a third ASI/feat has a lot less impact than delaying a first, and cherry picking to 2nd or 3rd level doesn't mean you don't have the main parts and level 5 power bump from other class(es). Cherry picking things that scale well, such as the Peace domain that scales with proficiency, or a class just to get Shield/Absorb Elements/Silvery Barbs.
Party synergy is more important than any character build. And a common issue I see when people build high level characters for one shots instead of characters that started at low levels and grew together is that they don't really have it. Coming in at 12th so many of your character choices have already been made. I would ask the DM to allow character tweaking for the first couple of sessions as you learn the other characters.
At these levels the party has a lot more in it's bag of tricks. Casting/ritual use of divination spells daily for instance. It should change how play flows to some degree.
For the DM, characters will have lots of high level spells. If they don't do enough encounters per day to run the casters down to a good amount of cantrip/low level offensive spell usage (vs. utility/defensive), then the long-rest recovery classes like pure casters will dominate the other classes.
At higher levels, common use of things like Simulacrum to double up casting, "microwaving" opponents (holding them in place and kill just standing there, such as forcecage plus heat metal or sickening radiance. And don't forget frequent conjured allies for meat shields and damage.
Multiclassing has more payoff - delaying a third ASI/feat has a lot less impact than delaying a first, and cherry picking to 2nd or 3rd level doesn't mean you don't have the main parts and level 5 power bump from other class(es). Cherry picking things that scale well, such as the Peace domain that scales with proficiency, or a class just to get Shield/Absorb Elements/Silvery Barbs.