Defender

You can cast on a willing creature and a layer of magical force surrounds it until the spell ends. The target's base AC increases by 1 for 1 round. The spell can end early if you dismiss the spell as an action. When cast at a higher level, the AC increases by a further 1 for each level cast above level 1, and the AC reduces by 1 each round afterwards until the spell end. For instance, if cast at level 3, it raises the AC by 3 on the first round, 2 on the next round, and finishes by raising by 1 on the last round of the spell.