Like most Magic: The Gathering cards, the value of Abyssal Horror depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Urza's Saga)
VII restricts your choices to create flavor, as these are the five main creature species from Fallen Empires
Mewtwo Box Topper Reverse Holo Market Price: $129.91 The first of four Box Topper cards featured here was originally printed as a non-holo Black Star Promo (#12) with artwork from legendary Magic: The Gathering illustrator Christopher Rush, who was responsible for the artwork on instantly recognizable cards like Black Lotus, Lightning Bolt, Mana Leak and Rod of Ruin
You are likely to be spending a lot of money, particularly for some of the cards we mentioned earlier and so it is worth doing a bit of research first and only using trusted sources, even if it may be a little more expensive in the first place
Legality depends on the tournament format -- The Explorer can be legal in some formats and banned or restricted in others
Do you remember my article from last week about mana flood and mana screw