The Hall of Light is one of the elemental dungeons in the Cairos Dungeon, and the home of the Guardian of Light. Defeating the Guardian awards players with Essences of Light. The dungeon is open every Sunday.
The following is based on data gathered by players, as of Summoners War patch 3.2.1.[1] You can contribute by visiting SWARFARM and following their instructions!
Use defense reducing debuff and/or defense ignoring skills to pass through the boss' defense.
Bomb debuffs and Continuous Damage debuffs also ignore defense.
In case there is a tower that grants invincibility to the guardian, use skills that remove buffs from enemies. Otherwise, kill the tower first.
Group healer is advised (but be careful of the Disturb Recovery Crystal).
Bosses and towers are immune to inability effects.
The crystals on the way to boss deal massive ignore defense AOE damage (100* crystal level) but have extremely low speed, consider bring AOE stunners or ATB reducers if you can't kill them in time.
"Guardians of Light have monstrous Defense! However, they have very weak HP!"
"Continuous Damage effects and fixed damage cannot be reduced by Defense stats."
"Skills that decrease Defense can be fatal to Bosses that have high Defense."
"This Dungeon is open on Sundays. From here you can collect the Essence of Light."
Trivia
The day that the Hall is normally open corresponds to the day in English, Korean, Japanese, and (archaic) Chinese. Sunday = 日曜日 (일요일, iryoil) (にちようび, nichiyōbi); 日 = Sun