Dagger of Ragnar

You make a dagger made out of a hard material (Iron, Steel, Stone, ...). It appears in your hand. The dagger can be used like a normal dagger. The dagger does 1d4 piercing, fire or cold damage. The dagger explodes after 20 seconds in a 4 ftcube of 1d2 Acid or poison damage when it leaves your hand, the material gets lost. The caster can use an action to let it explode or stop it from exploding and reset the 20s.

This spell’s damage increases when you reach 5th level (dagger goes to 1d8, explosion to 1d6)11th level (dagger goes to 1d10 explosion to 1d8)17th level (dagger goes to 1d10+2 explosion to 1d8+4)