Heated Caster (5e Feat)
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Prerequisites: The ability to cast at least 5 Fire-based Evocation spells.
Your intense study of fire magic has attuned you to the nature of heat.
You can affect lava and other heat sources (Magma is also lava for this) with your spells, treating them like fire as the spell requires. For example, this might mean you can use Control Flames on ambient heat or lava to make it dissipate or move. Electric sources ignore this feat. Fire and heat sources that are solid objects (Such as wood) aren't affected.
Finally, if you are attacked by a fire-based spell or effect (Or forced to make a save against such a spell or effect), you can use your reaction to force the attacker to succeed on a Wisdom saving throw against your spell save DC or miss (Area spells still affect the same area, except just around you. This is not enough to help anyone else.). This is before they (Or you) roll, and if they succeed by 2 or less then they have disadvantage on the attack (Or you have advantage on the save).
Warning: If you don't have 5 fire Evocation spells memorized for any reason, you can no longer use this feat until you meet it's requirements again. You still have the feat, it simply doesn't work.