League night is mixed faction upgrades which is creating a lot of headaches with regards to timing. If I'm flying Bossk with HLC and Bistan, could I roll four hits with HLC, change one to a crit with Bistan, then change that crit into two more hits with Bossk? 5 Hits?

Yes with caveats.

Heavy Laser Cannon's effect only happens after the initial role of the dice. Roll, turn any Crits to Hits, then proceed as normal with all dice modifications--the defender can modify the attacker's dice if they have any abilities, then you'll have a chance to use effects like Bistan to turn a hit to a crit at Range 2 (Bistan and HLC only overlap at Range 2).

Bossk happens at a slightly different time: after an attack hits. So it's kinda 5 hits if you'd rolled 4 initially, but not exactly. For example, Bossk rolls 3 hits and a crit against a Countess Ryad or Soontir Fel or Corran Horn or anyone else with three green dice, Focus token, and Evade token. So if I'm defending against this Bossk, I'll roll my dice before he can split the crit into two hits, and I might be able to roll the four evades needed. So Bossk isn't so much "five hits" as he's "four hits, plus one more." Getting four evades is less likely, but Bossk sometimes has a bad roll. If Bossk only rolled 1 hit 1 crit, the defender only needs two evades to prevent all Bossk's damage. But if the defender rolls no evades, Bossk can split that crit, and the defender takes 3 damage.

(I'll add another Caveat that the 2nd Edition Heavy Laser Cannon behaves differently, and turns all crits to hits *after* all dice modification, but that's kind of a whole different game that technically doesn't exist yet).

I disagree with your second scenerio. If Boosk Rolls 1 hit and 1 crit, and the defender rolls 2 evades, Boosk can split the crit into 2 hits and 1 hit will go through.

13 minutes ago, WhisperEcho said:

I disagree with your second scenerio. If Boosk Rolls 1 hit and 1 crit, and the defender rolls 2 evades, Boosk can split the crit into 2 hits and 1 hit will go through.

You are wrong.

Bossk's ability takes place after the Compare Results step in which evades cancel hits/crits. If there are no crits left at that point, his ability cannot trigger. This is in the FAQ IIRC.

1 hour ago, WhisperEcho said:

I disagree with your second scenerio. If Boosk Rolls 1 hit and 1 crit, and the defender rolls 2 evades, Boosk can split the crit into 2 hits and 1 hit will go through.

This is incorrect. Bossk clearly states that the attack must hit before he can use his ability. For an attack to hit, there must be uncancelled hit or crit results. In my example, both hit and crit are cancelled by evade results, and the attack misses.

Here's your three timing windows:

• Roll HLC attack...
  • ...then HLC converts all hits to crits right now.
• Once it's time to modify attack dice...
  • ...then Bistan can convert a focus to a crit.
• After the defender rolls & modifies, you compare results, to see if the attack hits...
  • ...then Bossk can cancel one Crit to add two Hits.
• Deal Damage!