Giving skeletons a fire arrows skill gives them the fire tag.
Giving skeletons a cold arrows skill gives them the cold tag.
Giving zombies the ability to vomit gives them the poison tag and the Damage-Over-Time (DOT) tag.
Giving Death Knights the death blossom skill gives them the Spell tag (note: This means they count as spell casting minions for purposes of things like Raven Roost giving +2 to spell casting minions, not that your Summon Mages skill counts as a spell. And yes, they do originally lose the spell tag from skeletal mages when converted to death knights. Giving them the death blossom skill makes them get it back).
So why does the Abomination get NO TAGS from ANY OF ITS NODES WHATSOEVER?
It can get a poison aura! But that doesnt’ give it the Poison nor Damage Over Time tags. It can get a bow skill. But that doesn’t give it the Bow tag. It can get a skill that converts ALL its normal melee attacks into a necrosis attack. But it doesn’t get the Necrosis tag from that. It can get its own hungering souls spell. But it doesn’t get the Spell tag from that.
This is inconsistent with every other necro minion where giving them a skill gives them the tag related to the skill.