There are a number of boss encounters in the Trial of the Crusader:
*The Beasts of Northrend encounter, which is made up of three sub-encounters
-Gormok the Impaler, a magnataur
-Acidmaw and Dreadscale, a pair of jormungar
-Icehowl, a wendigo
*Lord Jaraxxus, a man'ari eredar
*The Faction Champions, a PvP-styled encounter against a team of the opposite faction
-Eydis Darkbane and Fjola Lightbane, the Twin Val'kyr
*Anub'arak, a surprise fifth encounter that raid parties are dropped in upon