You will occasionally encounter pathways in dungeons that are filled with poison. You may consider buying the app that reduces and eventually eliminates taking damage from poison, but there is an easier way of dealing with them. Repeatedly press X (weapon swing) to move a step forward, but take no damage from poisoned terrain. This only works in dungeons and not on the world map.
Chaos ending
Side with Lucifer in "Armageddon".
God ending
Side with Dagda in 7/8 Moon.
Horde Battle
A fact not mentioned in the game is how the enemies of the Horde Race are somewhat weak to attacks that hit all enemies. Because Hordes are detected as being five enemies for the game's targeting system, despite sharing one unified set of statistics like HP and MP, you can use attacks that hit all enemies (such as Critical Wave, Mazio, Maragi, and Mabufu) to hit these Hordes multiple times. This technique is able to far exceed the power of your basic Attacks and numerous other Skills on many occasions by at least triple their norm, and is even more useful if you use a Skill element that the enemy is weak to.