Mythic Categories

While mythics are extremely strong units, more mythics does not always mean easier wins. Every mythic in the game serves one or more purposes. This is not a deep dive into all the mythics that fit each role, but rather a quick overview of those roles. To make this easier, I also rank each mythic in each section based on their ability to perform at higher difficulties. There may be biases, but I tried my best to make this list as accurate as a tier list can be, having seen all of them extensively in all the different modes and difficulties.

Wave Carries

These are the most popular mythics in the game because their strengths are immediately obvious as soon as you get them. Batman and Rocket Chu are two examples of this. Any mythic that clears groups of enemies with AOE attacks are Wave Carries. Some are good for the whole game, some are only good for the first 20 or 30 waves. But these are required to survive the main waves.

S Tier

Rocket Chu
Lazy Taoist

A Tier

Master Kun
Batman
Lancelot
Verdee
Drain
Iron Meow V2

B Tier

Frog Prince

C Tier

Tar
Iron Meow v1
Dragon
Bomba

F Tier

Ninja
Blob

Boss Killers

These mythics don't always stand out right away as being particularly effective. In normal mode, you won't need them. But when it comes to taking down bosses in hard mode and beyond you'll need them.

Note: Despite these units being great at killing bosses, the only boss killers that are able to clear dungeon are Vayne and Zap. The others won't be able to clear dungeon.

Note: Many wave clears will handle a majority of the boss fights. In general, you'll only need a specialized boss killer for the last few boss fights on the harder difficulties.

S Tier

Lancelot
Vayne
Watt

D Tier

Support

Support mythics do things other than dealing damage. Some are strictly support, like Kitty Mage. Some are hybrid, like Iron Meow. But they add a different value to the team. Kitty Mage and Iron Meow increase MP Regen. Monopoly Man gives lucky coin generation and Defense Reduce. Stun mythics also belong here, such as Orc Shaman.

S Tier

Kitty Mage (Get this to level 12 as soon as possible!)
Indy
Monopoly Man

A Tier

Orc Shaman

B Tier

Coldy

D Tier

Mama

Mythic Stuns

At first, these units are outclassed by the standard blue and purple stun robots. That being said, they have their purposes at higher levels and with their exclusive treasures unlocked. Grav is popular to get 100% stun lock in hell, Orc Shaman buffs physical damage with his exclusive treasure, and Pulse Generator has become more common in the top-level Korean Lucky Defense community as of late, due to having good slow with it's exclusive treasure, and doing high damage relative to the other stuns for wave 20/30 in hell.

A Tier

Graviton
Orc Shaman
Pulse Generator

Conclusion

These are the main categories in the game. Keep them in mind when choosing between mythics to summon. If you have Wave Clear covered, consider trying to get more boss focused DPS. If both are covered, you can scale them into the late game by adding some support units. Try different blends of units. Even months into the game you're likely to find units you had thought were useless in the past are good under the right circumstances. Understand the full kit of mythics and you'll find the game leans less on luck, and more on an understanding of what to do with the tools you're given.

Good luck!