Toxic orb

A globule of poison flies towards an enemy within range. make a spell attack on a hit do 1d4 poison damage and the enemy rolls a constitution saving throw. On a failed save the enemy is poisoned until the start of your next turn. 

The spell's damage increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4). and gains an extra round of poison when you reach 11th level.