Background.A captain of the Serrated Suns chapter of the Word Bearers and also one of the first of the Word Bearers to look into the depths of the Eye of Terror -- he discovered that it looked back at him. The daemon, Raum, possessed him (or arguably formed a symbiosis with him) and enabled him to transform into an incredible part daemon entity capable of mass destruction on the battlefield.
Purely aside from me, he was also best buddies with Kharn, and the two enjoyed a strong friendship until the end. At which point Kharn was rightly angry...
The stat line along for Argel Tal is very attractive with 5's all round apart from 4 wounds and an extra pip in WS. Combine this with a natural 2+ save and the daemon special rule means that this is an HQ choice to be reckoned with. His close combat attacks feature AP3 at S+1 which means he can pump out a huge amount of damage in melee. The rending and shred rules merely add to this deadliness level.
I find the warlord trait, Master of the Vakrah Jal, to be very interesting indeed. Using this, Argel Tal unlocks Gal Vorbak as troops choices. If the unit that Tal joins are made of models that have the daemon rule, then they all get feel no pain too. This can be really strong overall, and encourages a really interesting army composition.
He is not a scoring unit, nor does Tal have any ranged weaponry (except for the standard grenades). Naturally, he's also only available to the traitor faction.
Curiously, Tal lacks the Word Bearers Astartes special rule, but this is understandable. This does not affect his ability to be a praetor level character and select a rite of war from the Word Bearers list though.
Other than that, the player will need to consider how to get Tal where he needs to be.
Argel Tal is a very strong close combat HQ choice for the Word Bearers legion. An army with lots of daemons in and Gal Vorbak is frankly frightening from a number of different angles. But that sort of army requires finesse to make work well.