Akademeia garden: 2 melee 2 ranged mob, melee pretty high hp/def, ranged snipes if they get sethed or combos is very deadly.
Eternal ravine: 2 boss left and right side, blue worms has hax hp drain must kill first, blue spider thing can res.
Altar of giant cubes: 5 boss + main boss, cubes high def, main boss is really hard and is a gunner usually takes out a whole column.
To go in to Eternal ravine you need cube shards which you get from any 3 of the cube rooms from forgotten patrol they have high hp/def and hax light slash. You don't have to clear the cube rooms so all you do is run in and kill all the forgotten patrol and boss at the center until you get enough cube shards.
Valley is very easy if you have cube shard and can solo. 4 105+ soloer can finish within 60~90min. Recommended for 100+ (5~8 ppl).