You can find Temple of the Jade Serpent dungeon within the temple.
The coordinates are (55.5,57.6)
Attack the Corrupted Scroll to start the 2nd boss fight.
In Terrace of the Twin Dragons kill the sha mobs attacking the Serpent Warriors (3 groups) then the 3rd boss will spawn.
1. Wise Mari
/i Move to back of room and kill all adds (ignore boss here). When Corrupt Living Water dies move out of sha puddle they leave. Boss bursts his protective bubble & channels a beam of water. The water rotates in a circle, avoid this & kill boss.
2. Lorewalker Stonestep
/i Will fight either Trial of Yaungol (Strife & Peril spawn. Attack 1 until hits 10 stacks of Intensity, when turns to Ultimate Power switch to other & repeat). or Champion of Five Suns (attack 4 suns, when one dies sha spawn. Defeat Zao when corrupted).
3. Liu Flameheart
/i Dispel Serpent Strike. Stay spread, avoid fire waves. At 70% Jade Serpent Dance puts additional effects onto her spells (includes knockbacks,fire patches). At 30% summons Yu’lon, focus kill dragon. Avoid green fireballs that leave pool on floor.
4. Sha of Doubt
/i Dispel Touch of Nothingness. Wither Will inflicts shadow damage to random players. During Gathering Doubt kill all the copies of players before they explode, if they explode will deal damage & heal boss.