Disgaeaheim

Valheim, with Disgaea 5 Complete inside it. You play Valheim; Disgaea 5's real heroes, monsters, items, evilities, music and voices come straight from your own installed copy.

• Gear levels. Every weapon and armor piece levels up to Lv 9,999 from hits and kills, attuned to a real Disgaea 5 item of its kind, and unlocks Disgaea evilities (Muscle Increase, Fatal Hit, Breath of Life...) every 25 levels.
• Item World. Press K with a weapon equipped and dive into it: floating floors of Prinnies, Imps, Orcs, Succubi, Dragons and more, with Disgaea 5's soundtrack. Every cleared floor levels the weapon; every 10th floor a Disgaea hero is the boss.
• 28 heroes from Disgaea 1-5. Beat them in the Item World and they join you: Laharl, Etna, Flonne, Adell, Rozalin, Mao, Raspberyl, Valvatorez, Fenrich, Killia, Usalia and more. Press Y for their own Disgaea specials (Overlord's Wrath, Sexy Beam...), in their own voices.
• Prinny squad. Prinnies follow you and fight. Lift one with G, throw it with G. It explodes, dood (and reincarnates).
• Chores. From the roster (H) send heroes and Prinnies to gather, tend fires and smelters, farm and cook, or run Item World floors on gear left in a chest.
• Disgaea numbers. Wild Valheim enemies get Netherworld levels by biome, and damage numbers get Disgaea-sized.
• Co-op. Play with up to 10 friends. Host with Start server; Melty shows friends the join code to enter under Join game → Join by code. Friends near you dive into the Item World with you.

You need: Valheim and Disgaea 5 Complete installed (Steam). Nothing from either game is shipped; the mashup reads your own copies.