SoRCon 11 23-25 Feb 2018 Basildon UK http://www.sorcon.co.uk
Let's say my opponent generates 5 earth power, 3 from a character and 2 from a booster. If I play a card that discards the booster, do I still have to beat the original power value of 5, or the power value from the remaining active cards (which is 3)?
The latter. Read the last sentence in the section Power Phase, on page 6 of the Rulebook, in particular the word "current".