My problem with Sadism is that it's exactly the same ability as Scavenger. Why the same ability but with different name? Makes no sense.
Furnace. It increases damage by 2. Again I ask why? You said that..
1. Furnace is extremely hot
2. You feed on this (heat?) which increases your power
3. You somehow channel this power (heat?) through you increasing the damage of your characters and spells
Lol what does that even mean?
Sounds like an episode of twilight zone. Why not just change the card name to something that would be easily understood?
Fireflies don't have flight? Um.. have you seen the picture? Can you see those WINGS? Fireflies most definitely DO have flight. Or are you saying they walk to battle?
Think about it like this: Fireflies can fly. You use the card "Flight" on them to make them be able to fly (although they already could). How does giving them the ability they already had, increase their damage?
And I'm not saying you should rename the ability to "Dive" because that wouldn't work either. Only creatures who can fly, can also dive (like Wyrm and Pegasus).