So, that's my ooc guidance to you as a player — on the IC front, if you want to take that route but can't justify it ICly (say, the character would be too cautious, but you're OOCly keen), we could say maybe the absorption is accidental — the spheres transform into liquid, the compulsion re-emerges, this time to drink some of the memory water, so on.

Taking on the memories would be like viewing a (really depressing, at times harrowing) movie, so it wouldn't generate the same kind of psychological impact as would experiencing them. The person who absorbs the memories (who needn't be Red, btw!) would know at all times they are not the person they happened to.

You could also check with some of the witch/sorcerer characters in the party, if anyone has any experience with memory spells (or equivalent) and could 'extract' the Matthias-relevant memory.

Your other option would be to go to a memory seller, turn over a part of the liquid (I advise keep some so people can retain memories upon leaving Akhuras, personally) and ask them to break up the memory flow into hundreds of individual memories, then view Matthias' unique memory. That could end up a bit costly, but they're pros at the job, and duress is always a choice :' )

If none of these options work, shout!