No, not an extremely power hungry human being, I never said such a thing thank you very much.
In my point of view, Syndra is an (once suppressed, now set free) omnipotent psycher. Simple as that.
She could easily seek otherworldy realms for power. It's just that when you reach the point of power not being a limit, you don't really give a damn about branding your specialty. You can evaporate people with the power of your thoughts, trivial things like a mark of power are pointless by this point. A necromancer on the other hand, a psycher who is bound by death, would have the need to clasify their power level. Since they are bound by their dark arts, and death, they have to mark their capabilities for their oponents to be aware they have achieved power that rivals death. Also, death is taboo for most societies as well as feared/misanderstood, so having a mark that states you have powers revolving what most consider "otherwordly" is an easy way to impose fear and make common folk respect your power(again, out of terror).
I didn't talk about Soraka because I thought 2 examples were enough, but since you want it, you'll get it honey:
Grim Reaper Soraka, keeps many of the characteristics that have to do with death as well as her basic aesthetics. Albeit a healer, she keeps her tool of the trade, her staff now turned a cythe shaped like a crecent moon, which fits her "starcall" thematic as well, since you know moon/night/stars that kinda stuff. It also looks similar to her stock staff, again, keeping the thematic real. Devil in many religions, especially Christianity, is symbolized by a goat. Most of Soraka's characteristis reseble a goat; her hooves, goat legs, horn, ears, all characteristics atributed to the Antichrist, Faun creatures, the god Dionysus from ancient Greece who inspired the Antichrist to beggin with. She might heal instead of killing, which I consider comedic irony, but don't forget her abilities can also damage. Also, they have runes and symbols that give a dark feeling instead of her usual healy-starry-fairy stuff as well as darker toned Heals. She is basically infusing with dark energies instead of pure vitality.
I never said skins are lore related thank you very much, the second thing you make up. Gotta fix that habit of yours.
I know Riot's confirmed it as well. What skins do however, is follow the Champions visual cues and thematics, which is the primary concern when it comes to readability in-game for Riot. One of the reasons spell effects get adjusted, skins get toned and recolored, and all these adjustments happen in the PBE. Dragon trainer Tristana does what Tristana would normally do, following her thematic. It has nothing to do with her lore. But she still is holding the dragon in her hands like her cannon. The dragon fires fireballs and flies in the air for her jump. She could be riding that dragon and fly across the map, and the dragon could fire piss at the enemies instead. The dragon could be a fully matured creature instead of a taimed youngling. But no, the skin follows her thematic and visual cues to the absolute.
Check yourself before you wreck yourself.