The biggest difference between a clan party and a party that was put together by ordinary players would be their ability to cooperate as a team as well as their ability to separate public from private interests. The strength of a clan, which had parties that could execute all orders without fail and march in step next to each other was not to be underestimated.
Whether it was their equipment or their morale, the players who were engaged with the Spectral Army remained inferior to the most renowned party known to everyone as the "Hundred Regiment" via the game's official website…
However, judging only from the party's line-up, how they alternately arranged the positions of different Classes within the formation, and the number of Elementalists present in their party, it was obvious that this was not the first time the party had laid siege to a Boss.