Battle of the titans

[Redhood101]

I’m planning my finale for my campaign. The group found a mechanical roc and I plan to have my final villain be a lick and a summoned dracolich. I’m guessing that the group will wake up the mechanical roc and sick it on the villains. My question is how do I keep the battle from just being them sitting back while their new pet beats all the baddies. Or to keep it interesting and not let the roc do all the damage.

[Ninjadeadbeard]

If it isn't too late, have them discover a set of pilot seats in the Mecha-Roc. They need to fly it into battle themselves! If it's too far gone, then have it distract the Dracolich. If the players just...let it have at the both of them, let it get obliterated by the BBEG and punish them with a righteous tpk.