Swarmlord card reads "creature * Behemoth"
But Brood Warriors are from the Leviathan Hivefleet.
Taking into account the other warlord is from the Behemoth hivefleet, as well as their troops, seems Swarmlord should read "creature * Leviathan"
Swarmlord Hivefleet
You're not the first to comment on this. It's discussed in the Chime of Eons article that deals with the Tyrannid Warlords.
Here's an extract
The Behemoth trait isn't so much inaccurate as out of date: all it indicates is when the Imperium first encountered him, not when he himself first saw action (as he is speculated to be immeasurably ancient, possibly older than humanity itself), and not where he is the present day setting.
I was talking about something more rule-oriented.
Hive fleets are like space marine chapters or ork clans. A way to name a group of tyranids and a trait to use somehow during the game. Not exactly what it is in the setting, but pretty close and acceptable.
PsiLAN,
To echo Feesh's comment:
The Swarmlord is a unique creature that is purer extension of the hive mind than almost any other biomorph, The common comparison is that the swarmlord is to a hive tyrant what a hive tyrant is to a termagaunt. Thus it is able to be mutated by all hivefleets, regardless of proximity, interaction, or absorbed material components when the hive mind deems a situation worthy of its presence.
It technically led the hive fleet behemoth assault on the ultramarines home system, where old one eye was also present, hence them both having the behemoth trait.
That being said, i totally agree with you that for rules sake he should have been given the leviathan keyword, for the reasons yall both mentioned.