In most cases, the spells won't show the projectile shot or part of the spell thrown.
Mod being used alongside other mods, will give modlist if needed.

What's your mod version? This happened to a few people on old versions.

Age-Of-Exile-1.16.3-1.7.6 is the file name, so I assume the version is 1.7.6

post a full log

I also have this problem both in singleplayer and server. Changing particle settings and graphics level in the client make no difference.

mc version: 1.16.3
fabric version: 0.6.1.51
age of empires version: 1.16.3-1.7.6

mod config paste here: https://pastebin.com/zFB2HvdJ
server log here: https://pastebin.com/qgcEZSus

Remove immersive portals and the issue should be fixed.

Remarkable, that fixed it exactly as predicted. How could you tell that was the problem?!

Because spells being invisible can only happen if you join a server with a different mod version or if you're using immersive portals, which always has problems with my mod. I did not find other similar bugs yet. So far the only 2 mods that cause big problems with mine are immersive portals and optifine/optifabric, and they tend to cause problems with all other mods.
I will add a chat on login warning in next update if you have that mod installed. I don't want to flat out put it as incompatible as the fabric's error messaging is really confusing.