Threat cap

As explained in the main article, Threat is built via using damage and healing abilities on mobs. Since threat is a number attached to each and every combatant, and there is no way to reduce this number save using threat-reduction moves (Cower, Soulshatter (warlock ability), etc.), it is possible for threat to go so high that it eventually hits a cap (currently at 20 million). When the highest-threat holder hits 20 million threat (usually the main tank), then he will not be able to generate more threat.

However, since nobody else can exceed 20 million threat, let alone the 22 million threat required to pull aggro, there is no way of switching aggro anymore save taunt abilities; hence it is actually an advantage to reach the threat cap, as it prevents any DPS from ever pulling.