[RPG] Would vampires ally themselves with other monsters

This is one of those situations where the players have to try to shape the combat. There are three major situation types where a dragon or dragon-like creature might land:

1. It is compelled to by the players.

This category includes solutions that range from magic that can hold the dragon's wings, to creating clouds of dangerous gases or acids to make the air unsafe. Anything of this sort of compulsion relies on directly attacking either thecreature or the space it's in to force it to land. Some DM's might allow players to attack the wings separately, for example.

2. It has a motive that it can't follow while airborne.

If the PCs have captured a dragon's treasure and are taking it through a system of tunnels, the dragon can't easily fly after them. It would have to crawl/dig, and so be easier prey. Treasure is a powerful motive for forcing the dragon to come to you, as are families (such as baby dragons) or other items the flying creature wants to protect. For birds, this includes nests. This method is about baiting the monster into a trap or ambush where the melee warriors can cause lots of damage.

3. It is hindered by terrain.

A dragon probably won't have a lair with enough space to escape from the PCs easily, as they tend to be in caves. Large birds might be caught in their nests, and then get stopped from getting into the air. Terrain is the players' best friend in this case, and they can shelter under rocks or in other enclosed spaces where the dragon has to land to attack them, or in some cases even to find them. Some unorthodox ways to do this include the players hiding in forests where the canopy stops flying creatures from reaching them. Strategies like this rely on the dragon being in terrain where it is at a disadvantage, and can be combined to devastating effect with strategy number 2.

This is my favorite spreadsheet: https://rpggeek.com/filepage/108409/bestiary

It lists every published monster to date, has around 20 columns of information about each one and has wonderful sorting features built in. It is updated within a week or two of each book being published.