You have an urge to sacrifice yourself. You've had it for as long as you can remember. Even when you were young, when you were still mortal, when you only had so much to give, your instinct was to give it all. That habit has brought you a lot of pain, but it's brought great wonder and joy as well. It has let you bridge the impossible and the real, more than once.
You suppose it was inevitable that you would give your life. You can only be thankful that the time came late enough that it was not the only life you have to give.
To call the creature which the Astral Rift disgorged 'large' does a disservice to the thing. The creature of such size that it did not exist within the landscape around it, it replaced the landscape. Its body poured out of the rift like a river down a waterfall, and in a matter of seconds it covered everything within the horizon, and even then it kept coming, as though there was a whole ocean of this one, singular beast on the other side. It took you less than a second to initially react, but none of your fastest responses seemed to meaningfully impede the thing. The Forebear's Blade scythed through the creature, but the fact that the wounds it left would not heal meant little when the flesh that was shorn free was but a tiny fraction of a fraction of the beast as a whole. Even the Grave Poison which the blade weeps, while effective in rotting away an expanding radius of flesh, was outpaced by the sheer expansion of the creature. This foe would demand more, it seemed.
You summoned Gisena from her Laboratory to begin analyzing the rift for closure, and then conjure up Verschlengorge up from the Feasting Hall where it is stored during downtime. The Devouring Armament was prodigious in its ability to consume resources, but thankfully it was equally prodigious in its ability to use those resources. Even after all this time it still wasn't completely restored, but it had made great progress in recovering lost power and functionality.
You rose up into the cockpit of the Armament as your sensoria seamlessly merged. It is almost inaccurate to say that piloting Verschlengorge was an action unto itself, rather than simply an augmentation of actions you take. Your synchronicity was nigh-perfect. Achieving that was no mean feat, but your investment has paid dividends more than once, and did so again now. You reached out with vast arms, and your hunger expanded out from you, a sickly green light passing over the abominable nightmarescape like the dawning of a pestilential sun. The rightful inhabitants of your Human Sphere were shielded from your baleful glow by an ingenious sorcery, a collaboration between your dreaming self and Gisena, and as such it's terrific desolation befell only your new foe.
The beast, from the far shores of its oceanic flesh to the astral fountain from which it sprung, withered with visible speed, paling and finally turning to ash. At just the same time, Gisen completed her work sealing the rift, and the work was, or rather, should have been complete.
Not even a whole minute had passed before another, even larger astral rift formed, nigh-on the very same spot, and which seemingly the very same flesh ocean flowed. A more permanent solution would be necessary.
You had traveled to the other side of an Astral Rift once before (not counting the world you originally departed from to arrive in the Voyaging Realm), though it was accidental. The place had been inhospitable to say the least, pervaded by a malevolence as if on an axiomatic level, actively hostile to your presence there. You had considered intentionally spending time there, as a way to channel your Decimation, a way of achieving another iota of mitigation, but your experience had soured the idea, at least until you had some means of shielding yourself from the place's hateful nature. Now, you were considering traveling to that alien space again, for an entirely other reason. If this thing wasn't going to quit just because you beat it back once, you were going to take the fight to it.
You dove through the flesh, parting it over your armor like water, through the rift. Instantly, you were assaulted by the same loathsome force, stronger than before, stronger by many times. You could feel it seething, bubbling in the spaces within you. It would kill you, it was only a matter of time. So, you wasted no time getting work.
You shone with your Decimation again, though this time you provoked it into hyperactivity. A mitigation technique you developed, a way to buy respite in the future at the cost of exacerbating your Curse in the present, though now it came in handy as a simple way to improve the ferocity of this weapon. Unfortunately, even at your maximum intensification, the Decimation's radius and speed were insufficient to slay the creature before you yourself were subdued by the malevolence of its home. With so little time, you turn to your strongest tool, albeit one you have not familiarized yourself with as much as you now wished. You took the plunge into Sleep, and then into Dream.
Your mind expanded, the world pulled until the threads from which it was woven became apparent. You dreamed, and your dreams touched the strings of the unpleasant place where you found yourself. You found the stinging threads of Decimation, and you took them, and you wove them, until they spanned the width, and height, and the world was permeated by them. You could almost feel them drinking in the lifeforce of the beast whose scale you now outmatched. Soon, the abomination was broken and dead. Soon, but too late. Your body now was too weak to awaken, and so you slumbered still, dreamed still. With the might you still had, you twisted the threads of Indenture holding you to your domain, drawing them taught, and pulling your torpid form back through the rift.
Gisena closed the rift not a moment after you returned through it, though she was unfortunately ill-equipped to remove your human form from within the cladding of Verschlengorge. So instead, the two of you slumbered where you fell. You were not unfamiliar with Outer Sorcery, fortunately, but it had never been your favorite means of administering your people's fortune. Nonetheless it was what you had, and so your dreams turned to your domain.