His enhanced senses let him see, smell, hear Ignis so much better that Gladio wondered how he had managed to stay away from him dying the full moon this long. He groans behind the other, voice buried between his shoulderblades, touching in an encouraging manner. One hand wraps around Ignis neglected cock, giving it a few strokes.

"It's okay Iggy, come for me, mate." He purrs out, and does everything he can to get him there. He knows the other will tense up, but those moments after, when he softens and becomes pliant...

That is what he is looking for, the opportunity to slip in his knot.