Hey, I'm not the dev, but just looking through the code what I gathered was:

1. The Berserker Charge tactic is dependent on both a. having a North Germanic culture commander commanding the flank, and b. at least 1% Heavy Infantry in the flank. It gives a x4 bonus to Berserker attack with no defense debuff, which makes it especially powerful.

2. Berserkers appear to be viable, so long as you can ♥♥♥♥ up some losses in the skirmish phase and never plan on routing. Compared to Heavy Infantry, they get -40% skirmish attack, +33% melee attack, +200% pursue attack, -50% skirmish defense, equal melee defense, -75% pursue defense.

3. Berserkers are under Heavy Infantry.

4. They are not required to trigger any tactics, but they do get buffed / debuffed by preexisting tactics. Some that stood out to me were:

Skirmish phase:
Shieldwall - usually you want to trigger this when using Heavy Infantry. Don't. This tactic makes Berserkers cry. They get an additional -50% defense with no bonus to attack. If you plan on using Berserkers, never mix in Archers.
Charge - no requirements to trigger, aside from 10 days into skirmish. Immediately sets the phase to melee and gives Berserkers +350% attack. Heavy Infantry get +120%.

Melee phase:
Advance - needs 1% Heavy Infantry to trigger. Gives +300% attack to both Berserkers and Heavy Infantry. Gives another +300% against enemies using Stand Fast class tactics. Beware charging enemies.
Berserker Charge - needs 1% Heavy Infantry to trigger. Gives +400% attack to Berserkers but only +360% attack and -50% defense for Heavy Infantry. Gives an additional +100% bonus against enemies using Advance class tactics. Beware enemies standing fast.

@el_nora: Thanks for answering. Somehow I don't get notifications when new discussions are opened.

Will the berserker get a unit model or at least find a way to set to a different model cuz it shows upas a genric archer unit

I'm not a 3d artist so making an entirely new model is kind of out of the question. One could use the heavy infantry model I guess. I'll have to take a look how thats done.

cool it was just a thought !