There are three skeleton lords and they all share the same HP bar. As soon as you enter, run to the right and take out the skeleton mage while they're still not ready. After defeating it, wait a bit and defeat the skeleton warriors that will spawn. The other two skeleton warriors have wide range and can use fireballs as ranged attacks but they're slow so its possible for you to outrun them. Run around and use the pillars as cover whenever you need to heal.
Once the spawns are defeated, take out the next skeleton lord and the warriors it will spawn upon defeat. Take out the last skeleton lord and make sure to defeat the skeleton wheel spawns before they get to move. They're fast and can be problematic if they hit you all at once.