My Research
Want to iterate on my build? Here's my reasoning!
Stats
111 STR is required for scratch + rallied elim for all (non-boss) enemies [1]
64 QCK is required to have 3 turns each at the start of the battle for all enemies (except Spellbound Golem and Mistral Minion which would need 68) [0][2]
Increasing either of these stats further makes little difference, so putting the rest in VIT is good [0][3]
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Stones & Elements
Scratch, rally, eliminate, berserker, and ambush are the base of this build. Also I highly recommend the scratcher NOT having eliminate. This will make it impossible to confuse the two scrappers, in turn meaning less thinking [0].
Contuse reduces enemy damage by 25% [4], which is nice when you're going against heavy-hitting bosses [0].
Element type for the eliminator doesn't matter much because they won't be doing any elemental damage. However, Fire is the best elemental defense in both the Golem Workshop and Forbidden Portal [5] so I included it in the guide.
Element type for the scratcher matters if you want to be able to use an elemental slash on bosses. An elemental slash that is strong against the boss will deal >800 damage, which is over twice the effectiveness of scratch [0].
Forbidden Portal's bosses are both weak to Shadow and Water attacks [6]. Golem Workshop's Stone Borer is weak to Water attacks; Golem Workshop's Frost Delver is weak to Shadow, but very strong against Water [7]. As such both Shadow and Water are good choices, but Water a bit less so due to the Frost Delver.
Haste would be useful for the eliminator in the first battle, because if you use haste right away you get your turn back, meaning a bit of free breath [0]. But I'm lazy so I don't do that.
Why shred? I like it, and there's probably an argument for using it, but the returns are small, so I don't feel like testing it.
Minor Health Potions aren't worth using because the bosses deal way more damage than those restore [0].
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References
[0] My own trial and error in the coliseum
[1]
Flight Rising Coliseum Skills and Enemy Stats - Click "Enemy requirement mode" and pick "Forbidden Portal"
[2]
Flight Rising Coliseum Skills and Enemy Stats - Click "Enemy stats mode" and pick "Golem Workshop"
[3]
Flight Rising Coliseum Skills and Enemy Stats - Click calculator mode
[4]
Battle Stones and Coliseum Builds
[5]
Simple Element per Venue
[6]
Terror Toad and
Fear Frog
[7]
Stone Borer and
Frost Delver