ToME: the Tales of Maj'Eyal

What class would ever want a one hander and a mindstar in the offhand? I've heard archers can equip a dagger/mindstar in the offhand, but aside from them, who would this actually benefit?

On my Archmage The best staff I found was one handed. Took quite a long time for me to realize I can offhand a mindstar. Happened to find a +13% fire APR and +20% fire damage mindstar which lasted me until beating the game.

Bulwarks, Berserkers, and Bow Archers cannot use offhand mindstars without sacrificing most of their class features, but anyone else potentially can. As for how useful it is, well, that's more subjective. The obvious first choice would be spellcasters with shortstaves who just want the passive wielder bonuses from their offhand slot. Outside of that, you'll have to experiment for yourself. I've never heard of anyone doing, say, a sword-and-mindstar Wyrmic, and my gut reaction would be that it's better to specialize, but I'd be interested to see the result.

Mindstars don't get a damage penalty like daggers do for being in the offhand.
So if you aren't investing in dual weapon combat, you aren't sacrificing much damage.

1h + mindstar is usually my preferred setup for Cursed until the Gaping Maw comes along.

I often put Serpent's Glare or Bloomsoul in my offhand as Rogue/Shadowblade/Marauder until I find a good dagger. Other than that, Mindslayers could probably succeed with a 2h/1h/mindstar setup with a str/wil/cun stat focus since the mindstar would end up doing more damage than a dagger.

Strength-based cursed or wyrmic who has found an awesome one-handed weapon and would rather have a bit more offense than a shield?

I also find mindstars in the offhand very good for cursed characters.

They have much better damage than a dagger, because cursed often have very high willpower, and the mindpower bonus prevents the gloom cloud effects from being resisted.

Furthermore, in the mid game, it is rather easy to pile up 'when wielder hits' bonuses. The eight(!) blows of the cursed->slaughter->frenzy can dish out a ton of damage. And if you have 'Cleave' active, often everyone around the enemy you're stalking dies as well.

And if you get 'I can carry the world' and 'Superpower' as prodigies, one-handers and mindstars become terrifying in the hands of cursed. As an added bonus, you get an extra curse level from the curse on the mindstar, without needed to invest an extra talent.

Hell, there are so many reasons to use a one-hander plus mindstar combo with a cursed character, that only a very nice two-hander makes me give it up.