Intelligent Weapon Help

[lordhack]

Hi everyone. I've always wanted to use an intelligent weapon in a game, and I've also always wanted to use a Marlith. I've decided to combine the two, and give my players a longsword possessed by the spirit of a Marlith. The PCs in my group are good, and hate demons, but its a post apocalypse game and they're all pragmatists, so what they end up trying to do with the weapon might be interesting. Plus, I plan on making the weapon loot first used against them by a Hobgoblin warlord, so the players might carry it around just to keep it out of the hands of evil, or to find some way to destroy it.

I'm wondering what sorts of powers I should give the sword. Currently, my PCs have just hit level 3, and don't have any magical items yet, so I might hold off on introducing it for a while. For the moment, I'm thinking of making it a +1 Dancing sword, and perhaps letting the players unlock some new capabilities if they're willing to do some quests for the sword. Thoughts? Has anyone used magic items with scaling powers in 5e before and it so, how did it work out?

[Erys]

Make it a defender to emulate the Marlith's uncanny parrying skills.

Though personally I wouldn't introduce it till later; scaling it from say lvl 5 could work well. They find it and its +1, either attack or AC; then at 10th it becomes +2... until it is fully unlocked at 15th.

[gfishfunk]

Have it possibly summon a Marlith on rare occasions using the demon summoning from the unearthed arcana. The Marlith is NOT controlled by the party, and will generally attack anything in front of it - but for practical purposes, it will tend to go after the party's enemies first or be summoned on the other side of the enemy lines.

[Zanthy1]

Have said warlord appear soon, but not a direct encounter. make him a nemesis so that when the players finally defeat him, around level 5-6, they take his sword as a trophy. I'd start out having it just be a +1 sword, maybe the the ability to talk? I also like the idea that on a critical hit, it does a bonus damaging ability, something dangerous though like a bonus 2d6 to the target, and 1d6 to the user (can be changed to fit player hp and such).