[ ] Bring in Ice Witches
Currently, the only Ice Witch that is likely to be present for the battle is Milica. If you travel to Kislev City, you could bring in additional Ice Witches on Shadowsteeds. Milica says there are at least two and perhaps as many as five Ice Witches in Kislev City that would be able to respond and could meaningfully contribute to a battle.
[ ] Find the Boyar
For some reason, the Athel Loren forces seem to be trying to lure in Boyar Kalashinivik and his rota. Boyar Kalashinivik should be somewhere on the road between Praag and Kislev. Intercept him and see if you can figure out what this is all about.
[ ] Scout the Shirokij
Of the forces here, only you would have any chance of moving unseen through the Shirokij. Use this to try to scout the enemy.
[ ] Urge an attack
From what little you know of Tzar Vladimir, it does seem like it might be preferable for the attack to be made under the command of Tsarevich Boris instead. Argue for the attack to begin before the Tzar arrives, while the gathered pulks are under Boris' authority.
[ ] Attempt a parlay
The Tsarevich can grant you the authority to negotiate with these intruders in the name of Kislev, though that's easier said than done. Attempt to make that happen without endangering yourself too much.
[ ] Contact Ostermark
The Tsarevich can grant you the authority to reach out to Ostermark to request their aid on behalf of Kislev, and their military is already mustered at Bechafen. Ride there and request Elector Count Hertwig pushes into the Shirokij from the south as Kislev's forces do so from the north.
[ ] Other (write in)