3.5/5 stars. Rounded down. The rules are good and Zardu has a near unique power to control others.
Background.
One of the first of the Word Bearers to fully embrace the new religion after the Censure of Monarchia. Zardu is described as fiery and fervent in his beliefs, and has handily shackled a pair of unfortunate battle brothers to his own will over time -- the so called blade slaves.
Strengths.
A reasonable stat line much like a centurion combines with a force weapon with S+2 and enhanced D on force. The panoply of flame helps with combat resolution but the real strength here to my mind is the Binder of Souls psychic power (he also gets breach the veil). Select an enemy model with Willpower of 7 or less and they're yours in the close combat that Zardu is also part of. Handy, and almost unique in the game.
Meanwhile the blade slaves (Anakatis Kul) come with plasma pistols and the famous blades which give AP=3 and breaching with Phage on Strength. The stat line is also attractive with T=5 and S=5. Solid meat shields for Zardu and I like the fact that they also explode!
Weaknesses.
I never quite know what to make of Zardu and his blade slaves. They are cute little compact unit and there is some attraction in having the psychic power to control others. But if I am being truly brutally honest, there's just better HQ selections for the Word Bearers.
Overall.
I think Zardu has his placed as the HQ of a corrupted army, and as the forefront character for a melee charge. Beyond that, I actually don't like him too much. The one time I saw him on the battlefield, I dealt with him through a combination of precision shots and pie plates. His blade slaves routed shortly after. Its a bit of a shrug from me - he is fine overall, but just not the first choice I think. Cheap enough to consider for a kill team to be clear.