1) Enhanced Smite:
effect: 50% of the damage rolled will be applied to opponents prayer & 50% to their HP. the user will also take 50% of any damage to their prayer.
This sounds too strong at first glance but would be balanced by the fact you would be doing a lot less damage to your target making their chance of escaping more likely. The pker would have to determine if they can smite their target and do enough damage within the TB time , the person fighting back will have more of an incentive as they can get 'free' smite damage and gain the advantage if played well.
it would also remove the reliability of taking multiple brews as food since the restore potions will be drained a lot more often.
it would also open the gates for more prayer drain mechanics in pvm if there is a more reliable way to damage shields.
2) Run energy smite - same effect as the above but for run energy.
3) Prayer that lets you recover run energy 2x faster : would be balanced by having a drain rate that prevents it being camped, should also not be flickable. overall it would be useful for maintaining run energy at a decent level when waiting for a boss to respawn.
4) a prayer that redirects damage to your stamina or prayer points : can be used in a pinch when low HP in pvp or pvm. downside of potentially being 0 prayer or run by the time you heal up, making you more vulnerable
Slightly different to prayer , but a new form of defensive magic as an upgrade to one of the spellbooks that reduces the effects of venom or burn/dragonfire effects, similar to how ward of arceuus defends against corruption.