It's like the opponent has suddenly gotten a Skiver with shroud. You will deal significantly reduced damage for 3 turns while taking an immense amount in return, with a priority target you cannot focus. These champions are placed into the first spot severely limiting your options to stun them (which results in them returning to your side, stunned - if it applies).

If it steals the main damage dealer (like a Helion or Shieldbreaker) you're in a massive lose-lose situation.

This is the bosses gimmick and by far her most dangerous move.

The only thing to watch out for her is her 'Song of Desire', which steals a party member for 2 turns. The boss itself is not dangerous at all and has no offensive attacks to watch out for. Cleave bosses are at least countered by riposte, but the Siren has no obvious strategy at all she's just a complete high- or low roll boss that either wipes your entire team without any effort, or does practically nothing.

This boss feels like there is no strategy involved in any way. People cheesed this by bringing the Antiquarian and always having her nabbed from your team - which would be of absolutely no harm. We all knew that previously the Siren would, with 75% certainty, take the lowest resist party member.

Siren tactics darkest dungeon