Board Thread:Questions and Answers/@comment-25294051-20150524201240/@comment-25209037-20150530094415

All buffs overwrite the previous ones used.

That said, the game calculates the changed values of things during and after the buff is cast, not retroactively.

Let us say you have Feeva and Zelnite. You used Feeva's SBB first in your squad, that means Feeva and the next units gets their BC/HC DC boosted to 70% (35% base chance). However, if you used Zelnite's SBB right after Feeva's, then the next units will get Zel's buff. The same way happens if Zel's SBB is used third, he'll overwrite the buffs on the 4th to 6th units, while the 2nd unit enjoys Feeva's buff. On the 2nd turn, the buff that'll stick is Zelnite's as well, so you'll have to use Feeva's SBB again to overwrite Zelnite's. This is the general truth for most BB/SBB buffs.

Spark buffs does overwrite the previous buff, but the damage calculation will be updated as well. For example, you used Rosetta's SBB first on your squad, they'll receive the 80% buff.Then you fire the next units' SBB and creates sparks, those sparks will enjoy the 80% increase, but when you use Elza's SBB, the following sparks that is produced (post-Elza SBB) will have the 70% buff instead of the 80% buff. Tazer's SBB is a unique case (I'm not sure yet if this is as Alim intended), his SBB's spark buff, despite the wording, is a self-buff that doesn't stack with other spark buffs. So let us say we have Tazer in Rieji's merry party, and Rosetta used her SBB first, and Tazer second, Tazer will only overwrite the spark buff for his own, and his spark damage will enjoy a 130% boost. But if Elza again used her SBB last, it will overwrite Tazer's own self-buff, and the following spark hits he creates will have Elza's 70% buff.

However, this is partially true for crit buffs. Though crit chance is also calced per hit, the modifier that is used is the latest crit buff. Meaning Colt's buff will be overwritten with Kuda's buff if Kuda's is fired after Colt's. Also, critical hits, once triggered, has the next following hits as critical hits. For example, Len w/Lexida got buffed with Colt's SBB. Each of Len's 50 hits gets a 70% (10% base + 60% buff) chance to trigger a critical hit, meaning he can have up 10 hits w/normal damage, then he triggers a critical hit on his 11th hit, the following hits after the 11th up to the 50th are all critical hits.

Now, for things that stack:

Item buffs stack with LS and BB/SBB buffs: Holy/Ares flutes stack with BC buffs. ATK/Brute elixers stack with ATK buffs, same way DEF/Titan exlixir stack with DEF buffs. Ares potion's buff will be respectively overwritten by the appropriate buff.

Conversion buffs stack with regular buffs: Aurelia's SBB buff will stack with Kanon/Kaito's buff.

Self buffs will stack with general buffs: Ultor's taunt, Seria and Karl's SBB self-buff will stack with other buffs. Exception to the rule: Execrated Fei & Tazer's SBB.

Now, the UBB question:

BB/SBB's will overwrite UBB's. Alim will apparently change this in the sense that UBB buffs will not be ovewritten by BB/SBBs. Meaning Feeva's 170% stat boost on UBB will not be overwritten by her BB stat boost. Quite a tricky fix this is for the game, since UBB mitigation buffs, like Mag's and Kanon's, will not be overwitten by the regular mitigation buffs, so mitigation might be the sole exception to that as well

Anyway, sorry for the longass post. Hope this helps.