I have created a mod that expands available Ward spells to Expert, and I am working on a Master Ward spell. I am not sure what effects it should have that would set it apart from the rest of the Wards.

For example, the Expert Ward spell simply ups the magnitude (cost is 110 when autocalculated) of both the magic resistance and AR to 100.

I'm look for ideas for master level effects, and I am also trying to think of a naming scheme for the Expert and Master level ward spells along the same lines as the lower tier spells (Lesser, Steadfast, Greater). Expert and Master Ward would suffice, but I would prefer something more creative.

A simple idea for the master ward is to add a healing magic effect so that the ward both protects and heals you while it's active. A slightly more complicated (in as much as it requires a tiny bit of scripting) is to make the ward either reflect incoming spells back to the original caster or unleash a FUS-like shockwave that staggers nearby opponents.

As for naming conventions, you could call the expert-level ward 'grand ward' (since in Oblivion the level after greater x was grand x). 'Grand' was unfortunately the last level so for the master-level ward you will have to be creative. If you go for the ward that reflects spells a lore-correct way to call such ward would be 'Shalidor's Mirror'. Shalidor was the (arch)mage who developed a spell capable of reflecting other spells.

Shalidor's Mirror...that's a good idea. Grand Ward also goes along with Grand Healing.

What "tiny bit of scripting" is needed to create the mirror effect?

Edit: Another good effect would be to somehow deflect arrows.

There is a deflect arrows perk in SkyRe iirc

I would also like to see Ward walls, where you could just set up like three of them for battle

Found a mod that adds a reflect spell damage effect. Seeing if I can incorporate that effect into the Master spell Shalidor's Mirror.