Act Mode is where the Master directly fights the monsters and fiends of Tanzra. To do so, the Master sends his essence into a statue of himself, which becomes his avatar. With this body, the Master sets out to rid the land of evil. Though the Master himself is eternal, his corporeal form is not.
There are two Acts in every area, each one culminating in a boss fight. One Act occurs right away, to make the land habitable. Once it's been cleared, a temple will be erected to serve as place of worship for the people. The second Act occurs after a significant event has happened in the story, usually accomplished by purging Monster Lairs first.
Note that the Score doesn't reset to the last checkpoint if the Master falls in battle. With careful application of Sources of Life, and perhaps a 1up loop, the Master can drive his score up really high.
The Master's combat abilities include a standing swing, a crouching swing, and a jumping swing, all of which have a decent arc. Also, if the Master is in freefall, hitting the attack button will cause him to strike the moment he hits ground, not in the air.
Each area has two Acts to clear through, with the completion of one leading to the other. However, the Acts (at least the first one) can be tackled in any order. Some acts are definitely tougher than others, but the only thing limiting progress is skill; there is no level-scaling system.
Act Mode is very similar to the original ActRaiser, but has been greatly expanded. The stages seem larger, more variety in monsters and their movesets, and the Master is a more agile and capable warrior.
The Master has a three-hit standing combo, an upward-leaping attack that easily combos into a second hit, and a crouching attack that not only avoids high-aiming attacks, but reduces incoming damage. As a trade-off, however, the Master's damage is also reduced by 50%. The Master also possesses a backdash to quickly evade attacks, which also comes with rather generous invincibility frames. The backdash does have a solid 1-2 second cooldown to limit its use.
The Master now has six spells to choose from, any of which can selected in situ by justing holding down the magic button. Here, spells use MP rather than Source of Magic scrolls.