If you google Queen Ileosa, you can find out a lot of bits and pieces about her past as a Chelaxian and her motives for coming to Korvosa in the first place. But I can't find the actual book where this information comes from, or I'm just reading over it.
I own the hardcover Curse of the Crimson Throne and the Guide to Korvosa. She doesn't get much attention in the Guide to Korvosa or the CotCT player's guide. She gets a lot of attention in the hardcover AP, but almost all of the information after the first few pages is about her role in the campaign and not about her past.
Am I just missing her biography somewhere in the hardcover book?
Is it in something else?
Incidentally, in her wiki, they say she was 30 when she died. When you match this up with information about her being less than a third of Eodred's age, it means the king was over 90. He really was pretty negligent about trying to get an heir.