Been away from my computer for a couple days, my brain was bored so I started thinking up the nastiest thing I could do with a solo Tachyon that needed her target dead no matter what. This seemed like the best topic to stick it, rather than make a new one about Tachyon.
At the start of Tachyon's turn, she has a move value of 6 with Lightspeed Barrage and Unrelenting Momentum in play.
1. Tachyon uses Lightspeed Barrage (remaining HP: 3)
2. Tachyon uses Sprint (remaining AP: 2, gain immediate free attack)
3. Tachyon uses the free attack, rolling 6 dice
4. Tachyon uses Lightspeed Barrage ( remaining HP: 2, gain immediate free Lightspeed Barrage)
5. Tachyon uses free Lightspeed Barrage. Not for any additional value, just because she can
6. Tachyon uses Sprint (remaining AP: 1, gain immediate free attack, gain immediate free Sprint)
7. Tachyon uses the free attack, rolling 6 dice
8. Tachyon uses the free Sprint (gain immediate free attack)
9. Tachyon uses the free attack, rolling 3 dice
10. Tachyon uses Lightspeed Barrage (remaining HP: 1)
11. Tachyon uses Sprint (remaining AP: 0, gain immediate free attack)
12. Tachyone uses the free attack, rolling 6 dice.
Assuming you start your turn within 2 hexes of a target with no hazard spaces (and assuming I understand the order of operations correctly), you can throw a total of 21 attack dice in a turn over the course of 4 attacks/12 actions. Did I get it right?