How do I add potion effects on mobs every time they step in a block

[TheRPGAdventurer]

   I need my nether dragon to be able to regenerate every time it steps on lava and magma block via regeneration II potion effect, every comment is appreciated.

 

[larsgerrits]

You could use one of the tick methods inside your Entity class to check if the Block below the Entity is lava or magma, and then apply the potion effect.