Apmos´ Reckless Charge

You charge at a foe with reckless abandon while coating your shield with radiant energy ready for a strike. As a bonus action you can move up to your walking speed in a straight line towards your target and make a melee spell attack. On a hit the target takes 2d6 radiant damage and if it is 1 size category bigger than you or smaller  it must succeed on a strength saving throw or be knocked prone. For every attack of oportunity you provoke the damage increases by 1d6 to a maximum of 4d6.

In addition, if one of your allies is within the target´s melee range and the target attacked it this round you have advantage on the attack.

At higher levels.  Both the initial damage and the maximum damage increase by 1d6 for each slot level above 1st.