Bitter Pact

An ancient reviled magic. An ethereal purple string connects the members of the bitter pact, and the spellcasters hands are wreathed in a purple glow. The spell must be connected to an ally to use. For the duration, the spells caster deals an extra 1d10 necrotic damage on all attacks. Additionally, the ally affected by the spell takes 1d8 points of necrotic damage every turn for the duration. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d10 and 1d8 respectively for each slot level above 1st.