race features:
Molten Core: You are resistant to fire damage and have advantage on saving throws against the effects of extreme cold.
Slow Crawl: Your base walking speed is reduced to 25 feet; however, you are immune to fire damage taken from hot surfaces and objects such as magma, lava or a weapon affected by the heat metal spell. You can also walk over molten rock as if it were solid.
Vent the Core: You know the Green-Flame Blade cantrip. When you reach 3rd level, you can cast the Aganazzar’s Scorcher spell once with this trait, requiring no material components, and you regain the ability to cast it this way when you finish a long rest. Constitution is your spellcasting ability for these spells.