through-victory-my-chains-are-tightened
He calls on His allies, and they abandon Him.
He orders His slaves forward, and they die without achieving anything of value.
He tries a dozen other gambits. Open portals from Avernus to the Abyss, to Abaddon, even to the First World, to sow enough chaos on the battlefield to perhaps change the outcome. Wish exploding squirrels on top of a demon lord quickly roused to unthinking fury. Launch attacks on Elysium and Nirvana, with magic or with His own presence, to draw off their forces or threaten something They value. Sacrifice His assets on mortal worlds, built up over millenia, to massacre the locals in sight of the Good gods, Who must exhaust their intervention budget to stop Him. Buy the assistance of every god in Creation, Anyone drawn by domain or by nature or by plain avarice to His cause; and promise them His wealth and His power, the greatest of any single god left in Creation; and when all else has failed He bargains with His own submission, with the few Lawful Evil gods who might suitably tyrannize Him.
Nothing works.
Demon lords and Horsemen ride to Avernus in their fury, and are vanquished. Nirvana stands as well-guarded as Heaven, and no part of Elysium can He find unwatched by Desna; and where He goes, She sends Her outsiders and Her alien squirrels with their fields, and what He destroys they remake. On mortal worlds across Creation, Gates open and squirrels pour out, preventing and undoing His slaves' work with contemptuous ease, beyond the intervention budget of Heaven, of anyone, because the squirrels do not come from Heaven and are not sent by it. The few gods who make compact with Him are not enough to stem the tide; those He might submit to, rather than be destroyed, are still not great enough to win, because They are not better at using His resources than He is Himself.
If Desna were losing a war for Her survival, She might decide to break the god-treaty regarding intervention budgets, go out in a blaze of glory to deny Her foe some great victory. He is Lawful, and He cannot.
There comes a time when He cannot afford to defend Avernus. He withdraws His remaining forces to Cocytus. It is closer to Nessus, and much easier to seal, and to defend.
Still the endless Wishes batter at His doorstep, and His supply of damned souls slowly dwindles as one by one they are kidnapped, and lost to Him.