You can run test fights of your boss, this could serve as an introduction or just to see what the PCs are capable off.
A great way to run these test fights is to have a fool-proof way of escaping. You might want to consider rewarding the players for these fight so it does not feel in vain.
Escaping
- Monstrous abilities, like vampires & other magical creates
- Copies & Clones of the boss, using magic
- Teleportation
- Using magical items to escape
As always, be prepared if things goes awry and let the players have their fantastic moments if they are clever.
Reference
E. Schea, M. (2018). Sly flourish’s return of the lazy dungeon master. Sly flourish shop
Highlights or timestamps
Return of the Lazy Dungeon Master Highlights
- Test fight can be a fun way to run boss encounters. Powerful villains might create clones or have a guaranteed way to escape if they’re defeated.
— ^189dad from Return of the Lazy Dungeon Master highlights