Fetchlands, Snapcaster Mage, Goyf, Cavern of Souls, etc fit this profile
However, it cant be used as a companion because its deck-building restriction changes the size of your starting deck
Horn Attack does 10 damage for a single water energy card and, as we saw on the previous turn, Waterfall does 30 damage for one water energy card and one colorless energy
Stalwart Unity gets Howling Mine
These new glimmers - and new tricks - could certainly open up the game in interesting ways, especially as more people get their hands on the new cards
But these numbers are deceptive, since a properly aggressive deck that can avoid or ignore the pain or exploit an early dungeon completion bonus will value the Tomb of Annihilation highest among all dungeons