The Random Secondary Target System (RSTS) is a system deployed by Blizzard to make certain encounters harder and more challenging. The system will target someone in a party or raid but the target is never the player who is highest on the aggro list.
The system is probably designed to make the encounters more dynamic, otherwise most of the encounters would be "normal" Tank and Spank.
Common abilities using Random Secondary Target System:
- Heavy Damage spells, most of the time not enough to kill a victim but enough to require attention from the healers.
- Other spells, like
[Silence], DoTs, and alike. - Charges, the mob/boss randomly
[Charge] players with various abilities after the [Charge] ranging from knockdowns to heavy damage.
Some encounters using Random Secondary Target System are:
- Gehennas (Shadow Bolt)
- Baron Geddon (The Living Bomb)
- Golemagg the Incinerator (Pyroblast)
More Random Secondary Target System encounters exist.