So far I played 2 Int Heroes with Holy and i'm curious about other Heroes (LC int lane, party team, ...) . I will edit this list once every day or two so we can have all effects at one place.
Inmortal if this guide is against any rule please delete this Thread.
Kael - Entangling Root: adds nice spell bonus damage, perhaps depends on Int or lvl or both - not sure, need confirmation.
This passive ability of Holy is showing in the item so it is not considered secret or hidden you can freely post about it on the forum.
I was thinking in making a guide myself since there are some abilities that have multiple effects and a few of them does not have text to see what are they doing. But seem players can get some fun by doing the guide and I can correct or complete some of the abilities or you can request the guide from me as well.
Kael Entangling Root: Deal damage based in Kael total mana and level of Entangling Root(each level increases mana ratio up to 0.54)
Necromancer ability buff units depending the target if you target a level 9 Skeleton Warrior it buff all skeleton warriors of any level permanently if you target level 9 Skeletal Mage you buff all the level 9 skeletal Mages others target buff the golem also if have another effect of increasing Necro intelligence that have a chance depending of the ability level have a 100% chance to increases Intelligence on level 1 and 100% chance to buff units on level 9 middle % on middle levels.
Wraith: suppose to deal a lot more damage on the Curse ability that attack random targets around this ability does not show a text since the damage is not based in a stat is always the same, the extra damage should come with a different special effect and you should notice a big different of damage by checking a boss with high health taking the ability without and with the item.(Note: I never test this ability so no idea if is really working)