Some of the more sought after (read: expensive) cards on this list are: The original five Phyrexian Praetors Ragavan, Nimble Pilferer Atraxa, Praetors' Voice Skithiryx, the Blight Dragon The Brothers' War The Brothers War was the first official printing of serialized cards, and it was hot out of the gates with all 63 of the cards on the Retro Artifacts bonus sheet included in their sketch printings
You gain X life and draw X cards, where X is that creature's power
The effect of Prismatic Undercurrents's last ability is cumulative with similar effects
Spend it on the right cards
If, for example, you sacrifice Edgar to pay an additional cost of the spell or Edgar is destroyed in response, the spell will still resolve normally
Switch your opponent with another play