You will get a new spell card at level 88 soon called "Celestial Calendar" that is one of the highest one hit myth spells you'll get in a while. After that you'll get one damage spell (as of right now) called "Mystic Colossus" which will be a myth damage all enemy spell. Those two are some of the high tier myth spells you can rely on. However, I really do not recommend using calendar for PVP because of it's high pip cost. I can tell you this right now basilisk will be a big friend of yours because of it's DOT effect. In fact it could also surpass a little bit of calendar's damage.
These are just my way of battling and you may have your own style.
