Spirit Elimination
Normal Spell
When monsters in the Graveyard are removed from play, remove monsters on your side of the field from play as substitutes. This card remains active until the end of the turn that it is activated. The substitutes remain removed from play.

If you were going to remove 1 light and 1 dark for chaos monsters, do you must have 1 light and 1 dark in the graveyard then use substitutes? Also do the substitues must be 1 dark and 1 light? Can you remove tokens from your side of the field for substitution? If cards prevent you from remove cards from graveyard such as "Necrovelly" is activate, can you use this card so you do not actually remove cards from graveyard but the field instead?

1. You do not have to have 1 light and 1 dark in the graveyard to special summon a chaos monster the turn that this card is activated. You can instead use the 1 light and 1 dark monster that you have on the field. The substitutes must be the correct ones.

2. Necrovalley prevents altering the graveyard. Since spirit elimination does not alter the graveyard, you can use it while Necrovalley is active.