Arcane Advantage

Hobgoblins martial prowess is so heavily ingrained into their society that they apply it to their casting. You are able to apply your martial training to your casting, gaining the following benefits:

• Increase your intelligence, wisdom or charisma by 1
• Once on each of your turns you can add 1d6 to a damage roll on a spell attack roll if they are within 5ft of one of your allies who isn't incapacitated. The damage increases to 2d6 at 5th level, 3d6 at 11th level and 4d6 at 17th level. This ability can only be used on a spell of at least 1st level. 
• When you cast a spell that causes damage or forces another creature to make a saving throw, you can make yourself and a number of allies equal to your proficiency bonus immune to the damage of your spell and they automatically succeed their saving throws against it. You can do this an equal amount of times to the modifier of the ability you increased with this feat.