>>54280271Raid bosses react to different triggers
HP:
5 stars and lower put up shield around 50% HP or less left. 6 stars around 60% and 7 stars are more specific but around 80 to 90%. NPCs's damage (albeit smaller than a human player's) while playing solo will trigger the shield.
Player fainting triggers shield too, the higher the stars the quicker they shield upon faint.
Time:
Depending on how much time is left on the time bar bosses will react either with an attack, opponents's buff clearing, debuff cleansing or stealing Tera orb charge
Players fainting will drain the time bar in increments of 5 seconds, doubling up each time another faint happens. NPCs fainting while playing solo won't drain the time bar
For the reasons above, people will try to tackle raids with level 100 Pokemons and whenever possible to try and set up as much damage as they can, if a OHKO is possible then it helps a bunch as it bypasses shielding and time triggers.
Lastly your level correlates with your NPC helpers while soloing, the higher your level the higher their levels
