u/Veksutin

I've long been interested in the Aberrant Mind subclass, and hope to play one in the near future. I think a really cool way to build it would be to go with an amethyst dragonborn, since amethyst dragons are (at least in FR lore) known for their affinity for psionics.

The 1/LR flight is great, you'll get resistance to Force and eventually Psychic which is pretty unique and non-overlapping with Absorb Elements, and most importantly, picking dragonborn enables you to take the Dragon Fear feat at level 4.

I think this feat has, post Fizban's, mostly received attention for builds with Extra Attack since you can substitute one attack to use Dragon Fear. But I think it's quite underrated for sorcerers, and they may even have the better case for using it. Not only does it increase CHA and use CHA for its DC, but the action to use it is not a spell. As your opener, you could therefore Quickened Spell your big concentration spell of choice, and use Dragon Fear on top of that for crazy control of the battle field right from round 1. Very elegant :)

I think sorcerers are uniquely poised to take the feat too, because aside from multiclassing which has its own opportunity cost, other full casters would usually want to be taking Resilient CON or War Caster at this level. Sorcs start out with CON save proficiency, so they obviously don't need the former, and the latter can wait (I would probably only take it at 12 or even 16, after maxing out CHA and possibly taking Resilient WIS).

What do you think?

I think you could make a pretty amazing barbarian/rogue with the thri-kreen, which lets you take full advantage of the race's various perks.

You could start with 17/16/14/8/10/8, to go unarmored with a 16 (18 with a shield) from the thri-kreen unarmored defense. Make sure to take stealth and athletics proficiency, as you'll have advantage on stealth all the time (some DMs might rule this does not apply if you are armored since it's your carapace granting the advantage, although the feature does not say that outright), and advantage on athletics while raging, for grapples when that's desired.

I'd go beast barbarian for the first 5 levels, leaving one of the main arms empty for claw attacks and grapples, one holding a shield, and the two secondary arms holding scimitars. At level 4 I would take Slasher to round out STR to 18. By level 5, you can make four attacks total (two claw attacks, a scimitar attack and a bonus action TWF attack), all benefitting from the rage damage bonus of course. With 4 attacks + Reckless Attack, crits will happen semi-regularly for the Slasher rider effect and eventually chunky Sneak Attacks. If you grapple someone with the claw hand, you can still do three scimitar attacks with your secondary arms against them.

Past level 5, I'd go into rogue and take expertise in stealth and athletics to really lean into those. The thri-kreen telepathy will be very handy when sneaking around. Not really sure about the subclass, Soul Knife would be cool but I don't think it works out too well unless the DM lets you use the psychic blades with your secondary arms. Either way, Sneak Attack is the main draw here, which you can trigger with your TWF attacks (and ofc can grant yourself advantage with Reckless Attack).

I think I would just keep progressing rogue from there, increasing Sneak Attack damage. Things like Uncanny Dodge will be great too, and Evasion synergizes with Danger Sense.

The main weakness of the character would be the trash mental saves (WIS in particular), and you should probably consider Resilient WIS at level 9 (barb 5 / rogue 4), even though it doesn't round WIS up to an even score. The character is also not great at range, but you could keep your shield on and use a sling probably, with extra attack + Sneak Attack using your 16 DEX. Not great, but better than nothing.

I think this might be one of the more effective barbarian/rogue combos. What do you think? Which rogue subclass would you go for?