Like its predecessor, the game takes you through the land of Minutia, defeating slugs on your way to Mt. Boom. Unlike the first game, however, instead of matching symbols to defeat the slugs, the Fiends are on their own attacking them, with the player helping by tapping at the slugs and environment to gain coins that can help level up the Fiends into their adult forms. Even when youre not playing, the Fiends are fighting, gaining coins even when the app is closed.
Another additional aspect to the game is portals, which starts you back at the beginning of the game, with the catch that you earn a special currency to buy gadgets that help power up your Fiends and gameplay experience.
Best Fiends Forever provides examples of:
- Adapted Out: Being a different gameplay style than the first game, many Fiends do not appear in the game, with only four per tribe showing up.
- Boss Battle: Some levels cap off with a giant slug that has a large amount of hit points and a timer that is slowly going down, causing the player to have to defeat them before the timer goes down. Defeating them will reward the player with a crate filled with items or a new Fiend.
- Cartoon Bomb: They can be bought for diamonds, and can be used for heavy damage towards the boss slugs. If the player is nearly at the edge of defeating the boss, and runs out of time, an option to use a bomb and finish them off is suggested in a pop-up.
- Dung Fu: Tantrums attack, being a dung beetle, is to roll up balls of dung to cannonball launch at the slugs.
- Embarrassing Superpower: Kwincys attack is to shoot out webbing from his rear, something that seems to embarrass him heavily, as he blushes whenever he does it.
- Fantastic Nuke: The shared power of the red Fiends. They create a large mushroom cloud explosion that can instantly defeat a slug, while creating a large chunk of damage on the boss slugs.
- Flaming Meteor: The shared power of the purple Fiends. They summon a barrage of meteors that pummel slugs for a short period of time, though with an increased damage chunk.
- Idle Game: The whole draw of the game is the fact it can be played outside of the app.
- Make Me Wanna Shout: Brittle, Lapoleon, and Edward all have sound-based abilities as their attack. Brittles is a sonic blast from her proboscis, Lapoleon has a traditional scream, and Edward has powerful belches fueled by his coconut water supply.
- Piñata Enemy:
- A variety of slugs are crate-like robots that take more taps to defeat, but give out a shower of coins in return.
- The yellow Fiend shared attack turns attacks on anything into these, each tap giving out bonus coins.
- Secret Path: Some sections of the maps have a glow to them, where the player has to break down an obstacle. Breaking it down reveals an alternate path to take, which contains a heavy amount of treasure chests in the location.
- Self-Deprecation: The official webpage takes a few stabs at itself, saying the game will cause you to "LOSE TOUCH with your family and friends!" and encouraging you to "RECOMMEND it to people you don't like!". Possibly, the point about having to learn basic math to calculate the damage your Fiends will inflict is written in the same tone as well.
- Shock and Awe: The shared power the blue Fiends have. It summons a lightning cloud that zaps at slugs for slightly increased damage over an extended period of time.
- Time-Limit Boss: The boss slug levels have a countdown timer that the mission needs to be finished by.
- Time Travel: The game uses portals to send the player back to the beginning of the game, losing their unlocked Fiends in the process, but keeping the upgrades and earning special currency at the same time to increase the upgrades.
- Vocal Dissonance: The Slug Queen, being simply model reskin of the standard boss slugs, has a deep and masculine voice when she gets attacked, the complete opposite of her slender and feminine design.