Hall of Trials 2nd Version ( After Revamp ) Normal Mode Astromancer Elena 8 A SSS Spirit Eye Celine

The main tips:

Take all or some of the special advantages if you can
Exhaust the boss as fast as possible to maximize damage and defense
Make sure that your heroes are quite sturdy
For better chance of survival, bring reliable healer or lifesteal heroes or both
Don't underestimate the enemy
Cleanse your heroes from debuffs as fast as possible and don't rely on buffs and debuffs too much
Bring at least one hero with a non attack skill and make sure that it is available in exhaustion mode to gain exclusive ability

The tips against Astromancer Elena Fourth Version:

Now, it's Setsuka's time! Cause every time any new hero's release, hall of trials' advantages & disadvantages will be set accordingly automatically. But as usual, it doesn't mean that you can't complete this without the new hero.
The special buff greatly increase damage from thief hero with fighting spirit. Well, just like Young Senya (soul weaver with fighting spirit), it is unusual for thief hero to have fighting spirit (usually warrior or ranger). Besides Setsuka, there is Twisted Eidolon Kayron.
The hero granted this special buff will land more damage based on fighting spirit. The more fighting spirit, the more damage landed. When attacked, the thief hero will get 35 fighting spirit. So, bringing Setsuka will be a great help.
Any focus will be nothing (won't increase). So, don't bring any hero with it except if it isn't matter for you.
Bring at least one hero with counterattacking stance (ex: Senya, Twisted Eidolon Kayron, Aria, Ervalen), no matter whether it is manually or automatically (make sure that it is a buff, not a passive skill) and place him at the front (to dispell cajole debuff which only will be inflicted on the foremost hero and can only be dispelled by counterattacking by counterattacking stance. By dispelling it, you will increase the gauge by 60%. By keeping it, you will increase combat readiness of all enemies by 100% every time the foremost hero uses a skill).
Ability to increase combat readiness is negated. So, bring fast heroes instead.
Don't rely on healing too much, cause its amount will be reduced.
The damage you will receive isn't very big. So, no need to focus on healing nor defending too much. But, don't underestimate it too.
No need for aoe attack, nor attacking minions.