How do you envision this Elder just before Eric acquired the Regency of Amber?
Bleys is ambitious. He's been biding his time for a long, long while, and it will be his moment soon enough.
It's a hard life being a middle son. You're not the oldest, the strongest, the smartest, the best swordfighter, the best general, the best sailor, the best hunter, the best magician, the best student, the best lover. But you can be second best, or third best, at a lot of things. And all your brothers, the ones who have spent all those years honing themselves into the very best at what they do? Well, you can always fight them where they're weakest. Because you don't have to be the best at everything. You just have to be better than the whoever it is you want to beat. At something.
That's not too hard, is it?
Bleys has plans (or has implemented plans) to ally with Fiona and Brand to get rid of Eric (and possibly Oberon). His full siblings are reasonably loyal to him, and in case of a split with Brand--impending or merely possible--he's certain he can bring Fiona along with him. After all, he doesn't have to be the most persuasive, just more persuasive than Brand.
Bleys is the major public face of the cabal in Amber at this time. Fiona's good, but she's a woman, and there are those who simply don't take her seriously because of her sex. That's their mistake, but Bleys is happy to use their weaknesses against them. Brand, well, Brand is just ... there's a reason why if it comes to that, Bleys will win his sister's loyalty.
Bleys has been cultivating his resources: Avernus, his siblings, his allies in Amber and elsewhere, the things of shadow he can throw at Eric. He's not quite ready yet to make his play. But his time is coming, oh yes, it's coming. And when it is here, well ... let those single-minded fool siblings of his do what they do best.
For King Bleys.
Assuming the character has no memory of his/her persona or of Amber (and only a subconscious imprint of his or her personality), how do you see your character living in a film noir setting?
Bleys owns a restaurant and bar on the waterfront, perhaps even on a pier over the water, like Galveston's Balinese Room. [named Club Montepulciano, after the Hooverphonic song] Also like the Balinese Room, Bleys has an illegal (or highly questionable) gambling joint in the back. In the Roaring Twenties, it would have had booze, too, but that's legal now so he can sell it up front.
Bleys dresses flashily and drives a nice car. He probably has a nice house too; he's never short of money. Not that you'd know where he lives, because he spends a lot of time at his place. He's a good gambler, not just at roulette and blackjack, but at betting on horses and such as well. He enjoys eating and drinking the best his place has to offer and smoking fine cigars. Often Bleys has a pretty girl on his arm, but he has handsome young men in his employ as well.
Everyone comes to Bleys' place. It's somewhere to see and be seen, with fine wine, fine food, and fine company. It's a little racy, or perhaps edgy--the sort of place you'd bring a mistress more than a wife--but it's not so outre that people are actually discouraged from coming. The sort of people who wouldn't come to Bleys' place are the sort of upright prudes you wouldn't want to have come anyway.
Bleys has a lot of friends and connections. His little black book is a collection of the most important people in town. He can't always get the police off your back, or arrange for something to go missing, or have someone taken care of, but he knows who to call to have those things done.
Bleys knows things. It's not always clear how he knows them, or from whom he learned them. He's quite willing to have a convenient bout of forgetfulness about that abortion your mistress had, or the $75,000 that's missing from the company pension fund. Of course, he might want you to do him a teensy little favor later, but that's the way the world works, anyway. The same goes for those inconvenient gambling debts you accumulated in the back room.
Bleys does have some scruples. For instance, he doesn't like to kill people. You lose the best carpets that way.
After fifty years, the character's memories are restored. How is your character changed?
[this is necessarily the short answer; the larger answer is, depends on how things go in game play, doesn't it?]
Assuming that this happens at the time of Eric's Regency, Bleys is rather annoyed. Someone has put something of a crimp in his plans for universal domination. Who did this to him and the others, and why? Not to mention how?
Not that one should completely focus one's energies on such things, when there are allies to be reconfirmed, preparations to rescue from a woeful state of disrepair, etc. But it's foolish to leave someone or something that can do that behind your back. Remember, you don't have to be readier for any contingency than any of your siblings, just ready enough--and readier than the unprepared.