Thick Magma is the third stage in Volkanos Volcano.
When the battle starts, save up money for Dragon Cat while stalling the Owlbrow with Macho and/or Wall. Along with Dragon, Wall, and Macho, spawn in Sexy Legs. Keep spawning these cats throughout the battle.
As your units attack the base, spawn in any other strong units such as Bahamut Cat for support. This stage is not much of a hassle.