The word "transform" applies no matter which side is currently showing
In a Two-Headed Giant game, Thermo-Alchemists activated ability deals 1 damage to each opponent, so each opposing team takes a total of 2 damage
Unfortunately, and somewhat unsurprisingly, however, not all of them are good
Not only does this synergize well with mana rocks and other artifacts with activated abilities, but it simultaneously functions as damage-based removal, a means of closing out a game, and a means of digging through your deck for key cards
You can also view these cards in the set's card image gallery
That's right, Wooded Foothills, Flooded Strand, Polluted Delta, Windswept Heath, and Bloodstained Mire all got reprints at Rare in Modern Horizons 3