While wearing the starfire protocol chest and using gift of the sun while you have fusion grenades equipped the result should give you three grenades but only give you two
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The exotic helmet for Titans. Helm of inmost light. It gives you two abilities in your skill tree so you can put on something else. Putting on the same skills as the helmet doesn't do anything. Starfire protocol acts in the same manner, although it binds fusion grenades and gift of the sun together. That's how I see it at least.