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Remember that, when you are transformed via Reshape Life, your 1 button does damage, stacks the damage-taken increase debuff, and interrupts. Use this to stop the Amber Monstrosity from casting its Amber Explosion. Your 2 button interrupts your own Amber Explosion.

Watch the timer on the Amber Monstrosity's Explosion, and make sure your 1 ability will be off cooldown when you need it to interrupt. 

The melee damage of the construct while you are transformed is fairly substantial, so make sure to autoattack your target.