How to Kill a Primal Treant

[susj]

The monster appears in the Ancient Curse Part 5. Have no idea on what can stop its regeneration. Tried all four elements, negative damage, cold iron weapon. All had no effect. Anyone knows how to kill them besides Story Mode?

[torotacoman]

On challenging difficulty, I waited til they were both laying down from damage and hit them with disintegrate to finish them off. This is the second time I've done the fight however, and it didn't take anything special to kill them the first time iirc. (at least I didn't finish them with a spell the first time anyway.)

[schu]

Cold iron weapon works for me.

[Shahadem]

https://youtu.be/8SlWegS2sS0