B3 of the Terra Cavern marks the return of Piscodemons, who you still can't run from. They should be a lot less dangerous now than they were in the Marsh Cave, but they can still dish out a decent amount of damage and shouldn't be taken lightly. A number of other new and dangerous enemies can appear here, so be on your guard. Wights hit a bit harder than Ghasts, but they're less likely to Paralyze because they only hit once, so they can be saved for last when encountered together (though a quick shot of Dia2 might not be a bad idea). Wraiths are another new type of Undead, though you may have fought them guarding treasure in the Western Keep. Their main advantage is high Evasion, so spells may be in order against them as well, if you can afford the spell slots. Cockatrices are extremely weak and don't deal any damage, but their attacks turn your party members to Stone, making them incredibly dangerous if you haven't invested in a few Gold Needles. This might be a good time to use up some of those spell slots you've saved. Finally there are the rare Ochre Jellies, which are relatively easy to kill but dish out a lot of damage.
Earth Cave B3 has a much simpler layout than B2 did. You start in the south and follow a counter-clockwise path back to where you started. A number of treasure rooms can be found on the outside of the path, including one in a branching path to the northeast. The VAMPIRE and RUBY await in a room at the end of the loop. Behind that room you'll find a plate covering the stairs down to B4.