You could say Ichigo was angry. He didn't enjoy being threatened. He enjoyed it even less when those precious to him were threatened.
Yes, you could say he was angry. The scars in the underground training ground were proof of that. After the angel had delivered his ultimatum, he had spent hours releasing his rage. Shortly afterwards, he went upstairs and went to bed.
He opened his eyes in his inner world to see Nashi, Kyoka Suigetsu, Zangetsu, Murcielago, and Arakiel all waiting for him.
"So... what's the plan, partner?"
"Haaaaaah," Ichigo sighed. "Aside from killing that thing, I don't know."
"Ichigo," Arakiel began. "Gabriel is not someone you can beat with pure power. Lasciel will be teaching Nel what she needs tonight, but your teaching is a little different. I'll show you when we get there. I'll guide you to the mountain in the morning. What you need to figure out now is how to willingly relinquish control to Nashi. I can't teach you when all you're focusing on is fighting."
"In the past, it has only been me taking control by force and you pushing me out. Now, we need to find synergy. Forcing control and accepting it are two very different things."
All night, the two of them practiced exchanging control. Ichigo tried to remember how it felt when Nashi would steal control from him, but it was impossible. His mind had hated that feeling so much he had repressed it in the depths of his memory. With the first method barred, they started from scratch. Slowly Ichigo relaxed his mind more and more, letting his iron mental defense melt away. After an hour they managed to transfer control for thirty seconds before his soul rejected Nashi. It was a start.
Ichigo opened his eyes as he awoke to his warm bed, Nel's soft form beside him. He pecked her on the cheek before sitting up. It was nine in the morning and there was a lot to do. He packed his bags and began gathering the strongest arrancar. Nel joined him after roughly half an hour.
The former espada had been training tirelessly, and even the ones without divine power could kill a basic angel reliably. After gathering his Soulsinger companions, he also brought along Halibel, Grimmjow, and Uryu. The True Guard joined them just before they were about to set out.
"Everyone ready?" Ichigo asked.
After a few nods, he tore a hole in reality and they traveled through the garganta. They came back to reality to see a snow-covered mountain. The peak broke through the clouds and was out of sight.
"You couldn't have let us out at the top?" Grimmjow complained.
"Hey, I did my best. Gabriel's power was so dense this was as close as I could get."
"Either way, we might as well get climbing."
And so they did. They dodged a few falling rocks, but the climb was mostly struggle-free. After roughly fifteen minutes they reached a plateau. Standing upon the plateau were two figures. They had pure white wings that tagged them as angels.
"Hey look! Some toys!" Grimmjow's voice brimmed with savage joy and a grin spread across his face. Halibel's face twisted slightly in disgust for a second before returning to its normal, emotionless expression.
"We can take care of this Ichigo," Halibel said. "You may continue ahead... Cascada!" She shot a jet of water at one of the angels as Grimmjow dashed at another. The others blinked ahead and continued running up a snowy path.
"Hahahaha! This is fun!" Grimmjow shouted. "Cero!" A blue ball of light began forming at his chin. It grew for a few moments until exploding forward, blowing his angel into the cliff face.
"Hunt, Tiburon!" Halibel was engulfed in water for a moment before it dispersed, revealing her ressureccion.
"Okay... Grind, Pantera!" Grimmjow raked his claws down his blade and, with a flash of light, transformed.
In a flash, the two were assaulting their respective angels. Grimmjow slashed with his claws, deep gashes appearing all over the angel. Halibel was throwing Cascada after Cascada at her angel, pounding it into the cliff face.
After a few moments the two heard the angels voices in unison: "Divine Evolution: Retribution Angel."
Two flashes of light flew from the indents in the cliff and clashed together. The resulting ball of light slowly dimmed into an enormous angel holding a vicious sword. The Angel opened its mouth, but no sound came out. Its sword began to glow red as the angel raised it. All sound vanished, and the world became silent – frozen in time. The angel swung its sword at supersonic speeds, and sound returned with a boom. It was so fast, neither espada had time to react. And Grimmjow was missing an arm.
He slowly looked down at it with wide eyes as blood dribbled down his side. He had flashbacks to when he had lost his arm to ichigo. It was like Nam part two, Angel boogaloo. And he didn't like it. With an explosion of Reiatsu, he screamed, "Garra de la Pantera!" His claws extended into blue reiatsu, and he swung his remaining arm in the angels direction.
Halibel, in turn, threw her power into a Cascada, launching it at the angel at the same time. Then she sliced a wound in her arm.
The two espada wiped some of their blood onto their hands and screamed in unison "Gran Rey Cero!" Two massive balls of light formed in their outstretched hands for a moment before they released their power. The Ceros, Cascada, and Garra de la Pantera all hit the angel at the same time, totally obliterating it's body. If they looked behind it, they would have seen perfectly round tunnels in the cliff face where the Ceros had punched through.
The two of them collapsed to the ground as the angel's body began to dissolve. Grimmjow passed out from loss of blood, so Halibel immediately cauterized the wound with scalding water. The two of them had done their part, so Halibel decided it was time to go home. She opened a garganta and, wishing Ichigo and the others luck, stepped through.
Ichigo felt the angels' spiritual pressure disappear like a flame that was blown out. Shortly afterwards, he felt a garganta open and the two espadas' spiritual pressure faded as well. Knowing they got home safely, he grinned. One more worry off his mind. As they approached another platuea, he unconsciously let off a pulse of reiatsu. He was bursting with excitement. He could feel the same thing from Kenpachi beside him. He had a feeling this was gonna be fun.