Slain text says Uldyssian's Memories, but that isn't the boss's name. Intended?
3rd Uldy stage - Radament - drops book of skill and completes act 2 quest if you haven't done so yet.
Edit: Stage 1 - Blood Raven memory also completed blood raven quest
Edit 2: pretty sure this was noted already but dying in uldy stages seems to fuck up your colors. died in stage 4 for what it's worth.
Edit3: Fighting Malthael in Khalimgrad just to fight him again in Judgment Day feels pretty stupid.
Also, all the new portal system is cool but its also annoying as shit given that sometimes you'll need different specs for the layered portal bosses. Doing Khalimgrad then needing a different setup to do Judgment Day feels shitty, let alone respeccing again for uldy stages/uldy. Dunno. If you wanna keep portal idea, then I think it should just be portal spawns after the boss dies instead of using a 30 sec cooldown skill .