He gets healed every time he steps on Stone Tile with lizard symbol.
Damage Taken From Elements
You can only fight this boss in teams of 4. It's recommended that your team consist of exactly 1 knight and 3 shooters. The Ravager spawns with 4 Greater Canopic Jars in the room and can summon Canopic Jars. Both of these will remain statically positioned but if The Ravager is moved away from the Canopic Jar he will summon new ones near him. To have any chance of defeating The Ravager, your shooters must defeat all the Greater Canopic Jars while the knight forces The Ravager to bring all the Canopic Jars closer to him. When all the Canopic Jars are bunched together, the knight should move so that The Ravager is out of the healing range of the Canopic Jars but is still in the range so that the jars will not despawn. When the positioning has been set up the team should focus on trapping and killing The Ravager. Do not allow him to move when set up. Preferably, the knight will be diagonal to The Ravager, and will have the boss trapped with Wild Growth Runes or Magic Wall Runes. The shooters should position themselves behind the knight when it is trapped, so that it will not escape the trap to attack another party member.