Two copies of this card actually does more damage than one (one card with a full field of continuous spells does 4x300 damage, which is 1200. Two cards reduce the number of continuous spells to 3, but doubles the damage, so it's 3x600, which is 1800). However, three copies does exactly the same amount of damage as two copies (Three cards triple the damage but reduce the number of continuous spells to 2, so it's 2x900, which is also 1800). However if your opponent has any continuous spells, three would indeed do more.
While you can use this card in a Crystal Beast deck, you can also use it against one.
Combined with multiple copies of "Dark Room of Nightmare", you can do up to 1800 damage with just one copy of this card.
Assuming that no other cards on the field inflict damage, the maximum amount of damage that can be inflicted with one copy of this card is 2700(9x300). With two copies, the maximum amount of damage is 4800 (8x600). With 3 copies, the maximum is 6300 (7x900).