(1) Effects of face-up LIGHT monsters are negated. (2) If this card destroys a LIGHT monster by battle, it can attack once again in a row.
The (1) Continuous Effect applies so long as Brain Golem is face-up on the field.
This effect only affects LIGHT monsters while they are face-up.
The (2) Trigger Effect activates in Substep 7 of the Damage Step (End of the Damage Step) when monsters marked for destruction by battle are sent to the GY.
If "Brain Golem" destroys a monster that was LIGHT on the field but is no longer LIGHT in the GY (because of "Scroll of Bewitchment" or "DNA Transplant") it can still attack once again.
The effect of "Sphere of Chaos" is negated if "Brain Golem" is on the field, so "Sphere of Chaos" is not treated as a LIGHT monster.
If "Brain Golem" becomes a LIGHT monster, its effect is negated but all other LIGHT monsters are applied normally.
"Brain Golem" only negates the effects of face-up LIGHT monsters on the field. If a monster is no longer face-up on the field, its effect is not negated by "Brain Golem".