Rage of Mages is 70% off and very cheap, made by the devs who made
Evil Islands, another classic (70% off). All Nival games kick ass and you should buy them.
Silent Storm is more tacticool than an RPG, but get that too at 70% off. They also made the best HoMM game which is the fifth, fuck you losers who claim otherwise, that is 75% off. I can't decide which of their games I like the most but if you want a strategy card-game hybrid then
Etherlords is up there and insanely inexpensive now at 70% off.
The Surge is 65% off, not dirt cheap, but not bad for scifi Dark Souls.
The Revenant is 75% off and basically free.
You want bang for your buck, hours of entertainment without feeling a wallet burn?
Anvil of Dawn is also 75% off.
You say you have played all the TES games, but have you mastered the BDSM fuck dungeon that is
Battlespire? That is the TES game for real men. 60% off and you're not giving too much money to Microsoft.
Want an old atmospheric CRPG that you've probably never played? Try
Soulbringer at 70% off, it used to be bundled with Planescape Torment back in the day.
Nox is a classic that was better than all the Diablo games past the first one. 75% off and if you like hack and slash games there is no excuse not to get it at this pricepoint.
If none of that does it for you then you might like a weeb dungeon crawler like
Mary Skelter, 70% off. More hardcore than pretty much anyone made by big Western companies in the last two decades or so.