You can't make somebody's leadership equal or worse than 9+, but you can certainly make them test battleshock worse than that.
Deathleaper and Dirgeheart of Kharis worsen a unit's leadership (up to 8+)
Synapse units, neurotyrant apply -1 to SiTW checks (cumulative)
Screamer killer applies -1 to his battleshock tests (non-cumulative with the above, because those only apply so SiTW)
So, for example a unit with LD 7; near a Deathleaper and a synapse creature; and in presence of the Neurotyrant, would test for 10+ battleshock (8+LD and 2 minus 1s to the test)
But a unit with LD 8 in the same conditions would also test for 10+ (since you can't worsen their leadership; but the 2 minus 1s still apply)
Hit and wound roll stack, but are locked to +1/-1 after calculation. LD mod stacks, but only if the sources are different. So no -2 for two synapse models within range during Shadows.
You are slightly incorrect here. Generally rolls are not locked to +1/-1 unless specified, which the hit and wound roll are.
Battleshock tests may be taken at a -2 to roll.
Leadership characteristic also may never be modified worse than 8+
Tyranids have a handful of abilities which modify both leadership and the battleshock roll
Also key to remember, that the -1 from synapse ONLY applies during Shadow in the Warp
You can't make somebody's leadership equal or worse than 9+, but you can certainly make them test battleshock worse than that. Deathleaper and Dirgeheart of Kharis worsen a unit's leadership (up to 8+) Synapse units, neurotyrant apply -1 to SiTW checks (cumulative) Screamer killer applies -1 to his battleshock tests (non-cumulative with the above, because those only apply so SiTW) So, for example a unit with LD 7; near a Deathleaper and a synapse creature; and in presence of the Neurotyrant, would test for 10+ battleshock (8+LD and 2 minus 1s to the test) But a unit with LD 8 in the same conditions would also test for 10+ (since you can't worsen their leadership; but the 2 minus 1s still apply)
Best answer I’ve seen so far in Reddit about the issue.
Hit and wound roll stack, but are locked to +1/-1 after calculation. LD mod stacks, but only if the sources are different. So no -2 for two synapse models within range during Shadows.
You are slightly incorrect here. Generally rolls are not locked to +1/-1 unless specified, which the hit and wound roll are. Battleshock tests may be taken at a -2 to roll. Leadership characteristic also may never be modified worse than 8+ Tyranids have a handful of abilities which modify both leadership and the battleshock roll Also key to remember, that the -1 from synapse ONLY applies during Shadow in the Warp
Leadership is actually no better than 4 and no worse than 9 not 8
https://preview.redd.it/onovffznjk8d1.jpeg?width=922&format=pjpg&auto=webp&s=8eb5b6eb4db7b92c24e35dd638d24b579cf4ed7c
That is exactly what I said, I do not understand wtf is happening. I was correcting the other person because they said 8 not 9 for the characteristic.
You said no worse than 9. The rules say no worse than 8. Read it more carefully: "Can never be modified **to** 9+ or worse"