The World's Strongest Grandfather

He conquered an empire. They killed him for it. He came back as an old man they're waiting to bury. Kaelen Vashtor ended a hundred years of war and never lost a battle in his life — right up until the one he didn't see coming: poisoned by the council he built to rule the empire he refused to keep for himself. He wakes up in another world, in another man's body — not a promising youth with a cheat system and a bright future, but a seventy-one-year-old duke everyone in the house is quietly relieved is dying. His children don't trust him. His grandchildren won't speak to him. One of them might be trying to finish the job. He can't lift a sword. He can barely stand. So instead of an academy, he picks a family, and does what he's always done best — not with strength, but with patience, ledgers, leverage, and a mind that once ran an empire now aimed at saving four broken kids and a duchy no one else believes can be saved. Nobody in this house knows what he used to be. They're about to find out what "the old duke who never leaves his mansion" actually means. A kingdom-building progression fantasy about hidden strength, earned trust, and a grandfather who is, very quietly, the most dangerous man alive.