When compared to the closest thing , the storm atronach , the ash guardian has 160 more health , and also 5 more damage , however the storm atronach has shock immunity , and a wider variety of spells , all of which are shock-based , to which there are very few enemies who have ressistance to , and even less immunity to , shock damage .
The ash guardian also costs 110 more mana to summon , and you need a heart stone for it to not turn on you , which are pretty scarce , and are required in a quest from Neloth , not to mention the staff crafting . The ash guardian is pretty unique , because it doesn't count towards your maximum summon limit , meaning you can have 2 and , with the Twin Souls perk , 3 conjured allies , but no more than one ash guardian , it also functions like a Thrall , because it only dissapears upon the depletion of it's health , but unlike other conjuration spells , it will stay where it first spawned , meaning it can't follow you through a dungeon after you use it to clear a single room , increasing the demand for the already scarce heart stones . So , with all that in mind , is the ash guardian a reliable spell ? Should anyone use this instead of any other conjuration spell ?
I personally think that the ash guardian spell is not worth it. In my opinion, it costs too much magicka for something that doesn't even follow you around. It's only really useful for closed spaces, and even then I significantly prefer the dremora lords because of their good damage. I would much rather have the Conjure Seeker spell because they actually follow you around and can use ranged attacks well. If my answer came too late, I apologize.