My allies get a +2 luck bonus from an invocation Steyven uses on you, can reroll a save/attack/skill/ability check (but then I have to recharge the invocation), and also can reroll 1s on saving throws (if within 30'). Finally, if all that fails, Steyven can use an immediate action to reroll again for you using his level + cha mod (+16) if you're within 30'.
You also get Bless (+1 morale att/fear saves) + 10 temporary hit points from another invocation that he can refresh as often as needed.
Maybe we should have a thread/post devoted to buffs/debuffs that will always be in effect, for quick reference.