Is there a way to change that useless desecration to a useful one? like Cast Speed or something useful for a mage build.

Still missing skill+,so mb dont waste any currency in this

Cast speed for example is a suffix, so it is possible to roll. Question is, are the potential costs for it greater than just buying a more fitting item or not.

omen of light is your friend. repeat until you hit

FYI, I opted out of buying an amulet with + levels of spells because I literally deal 10 million damage in like 3 seconds so I dont need it (I use a mana stacking build with Adonias ego and stuff). So before you suggest I buy another amulet, this amulet is literally a perfect fit for my build, aside from the desecration it is perfect.

I DO NOT need level to spell skills.

+5 to quality of all skills if that matters with your build. It’s a min max modifier

https://poe2db.tw/us/Amulets#ModifiersCalc

Under Desecrated Modifiers - Suffix using an omen of the Blackblooded/Liege/Sovereign could get you something you might want.

If you got money just spam omen of ligth, and desecreate again untill you get what you want

Absolutely pointless to use very expensive omens of light on an ammy which doesn't even have + skills. Here's how you craft an amulet for your build (assuming spellcaster):

1. buy a prefered base ammy with minimum item level 75 and 50 spirit (or whatever spirit you actually need if you're crafting for yourself, the lower the cheaper).

2. anul to 3 mods of which 1 is the spirit, desacrate (no need to reveal) ( there are other better ways to do this but for the sake of simplicity..)

3. use fracturing orb. Repeat steps 1-3 with new ammys until you fracture the spirit

4. anul to 1 mod

5. spam regular chaos orbs until you hit +3 skills you want (can take a couple thousand tries if unlucky. You can also finish the craft with roughly the next steps if you hit another +3 skills, sell for profit and start over)

6. use mana catalysts to full, activate omen of greater exaltation, omen of sinestral exaltation and omen of catalysing exaltation then hit a perf. exalted orb. With some luck, you get 2x mana prefixes. If total fail, you can perf. essence of enhancement and/or prefix desacrate. The ammy will still have value even without mana and can sell for profit

7. use speed/caster catalysts if you want a chance at cast speed, or any elemental catalyst if you want to play safer and want resistances. Then activate omen of greater exaltation and omen of catalysing exaltation, slam perf exalt.

8. if a little lucky, you made a great ammy. If very unlucky and all mods hit bad (unlikely) you can always yolo anul and restart or sell to recoup costs and start over

9. you can always try to snipe a bad affix with a sinestral/dextral desacration, much safer for prefixes since spirit is fractures though

10. you can also fracture +3 spell skills instead of spirit and chaos for spirit then, it will be a little cheaper but the ammy can't be sanctified for +4 skills and will have less value should you want to resell.

Funny how you get downvoted ngl

Just keep doing light + echos until you get something you want, if you hit + skills just sell it and buy one that works for you