This dagger is made from hundreds of interwoven rose petals for the hilt, and the blade made from dozens of long needle-like thorns sharpened as one blade.

You gain a +2 bonus to attack and damage rolls made with this magic weapon.

You can use an action to cause thick, black poison to coat the blade. The poison remains for 1 minute or until an attack using this weapon hits a creature. That creature must succeed on a DC 17 Constitution saving throw or take 4d10 poison damage and become poisoned for 1 minute. The dagger can't be used this way again until after a short or long rest.  The hundreds of thorns also make the wound hard to heal, causing 1d4 bleeding damage at the end of the target's turn (This can be stopped with a medicine check of DC 17, or magically healing at least 5 points of damage)

When you hit with this weapon you can cast Spike Growth as part of the Attack, making spikes shoot out of the target's body, causing pain and damage.  The DC to resist this effect is 17

For Spike Growth^^^(Mechanically how this works is, for every 5 ft. the target moves including through the air, it takes the Spike Growth damage, as long as the caster's concentration is not broken.  Flavor is all yours!)

Curse: Bloodthirsty Thorn- If the attuned wielder of this dagger goes an entire day (Dawn till Dusk) without drawing another person's blood(meaning inflicting at lease 1 point of damage), they are immediately subject to the dagger's damage plus poison damage, as well as being poisoned for an entire day.

Proficiency with a Dagger allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Poison, Bonus: Magic, Poisoned, Damage, Debuff, Combat, Finesse, Light, Thrown, Nick