I've been trying to right click like mad and it also has absorbed ender pearls, but it wont do teleportation or long teleportations at all, is this bugged or am i being stupid on how this works?

Well in that case this will need to be reported to midnight. I don't see a good reason why it should be swinging player's arm when another mod's item is right clicked and Ender staff needs to see if the player is swinging arm to not spawn multiple teleport projectiles. There would be a way to go around that on Reliquary side, but would require quite a few changes and I really don't like doing that because some other mod does weird things.

Simple right click once charged will throw an enderpearl like projectile that will teleport you. Just make sure that you are not set to wraith node mode as that only teleports you to the wraith node that the ender staff is set to.

Let me know if you have any issues with that and if so I will need more info like version, if there are other mods in the pack etc. Otherwise I will close this in a few days.

These are the mods i am using, so reliquary's version is in there, the forge version is forge-31.1.48

AppleSkin-mc1.15.2-forge-1.0.13.jar
AttributeFix-1.15.2-7.0.2.jar
BetterAdvancements-1.15.2-0.1.0.96.jar
Botania r1.15-382.jar
classicbar-3.0.2.jar
Clumps-5.0.2.jar
CreativeCore_v2.0.5_mc1.15.2.jar
curios-FORGE-1.15.2-2.0.2.2.jar
Cyclic-1.15.2-0.3.4.jar
DungeonCrawl-1.15.2-1.6.3.jar
EnhancedVisuals_v1.3.12_mc1.15.2.jar
EnigmaticLegacy-1.7.0.jar
flexible_skills-1.15.2-1.2.1-beta.jar
Hwyla-forge-1.10.8-B72_1.15.2.jar
industrial-foregoing-1.15.2-2.2.2-28d4a81.jar
jei-1.15.2-6.0.0.3.jar
journeymap-1.15.2-5.7.0beta1.jar
mahoutsukai-1.15.2-v1.15.17.jar
Mekanism-1.15.2-9.10.1.414.jar
MouseTweaks-2.13-mc1.15.1.jar
NetherPortalFix_1.15.2-6.0.0.jar
NomadicTents-1.15.2-11.0.0-beta.jar
noRecipeBook_v1.5.2formc1.15.2.jar
Patchouli-1.15.2-1.2-31.jar
prefab-1.5.0.4.jar
ProjectE-1.15.2-PE1.0.3B.jar
QuantumStorage-1.15.2-5.1.1.jar
Reliquary-1.15.2-1.3.4.984.jar
swingthroughgrass-1.15.2-1.4.0.jar
themidnight-0.5.7-2.jar
titanium-1.15.2-2.3.7.jar
tombstone-4.3.5-1.15.2.jar
useful_backpacks-1.15.2-1.9.4.63.jar
u_team_core-1.15.2-2.11.0.156.jar
Vampirism-1.15.2-1.6.0-alpha+20200421-1031.jar
Waystones_1.15.2-6.0.1.jar

And also the logs for client is spamming quite a lot of this:

[27huhtikuuta2020 00:13:42.817] [Render thread/ERROR] [net.minecraft.client.MainWindow/]: ########## GL ERROR ##########
[27huhtikuuta2020 00:13:42.817] [Render thread/ERROR] [net.minecraft.client.MainWindow/]: @ Pre render
[27huhtikuuta2020 00:13:42.817] [Render thread/ERROR] [net.minecraft.client.MainWindow/]: 65539: Invalid key -1

I have zero knowledge what that means... Unsure if any of this is helpful information, but.. If i see anything else that might help i will make another issue, uh.. Feel free to close this if the information isn't providing any help.

I don't immediately see anything in the list that should cause mod compatibility issues, but there are a few I haven't heard of / played with. However I don't have time to try figuring out which one may be causing issues for you. If you can narrow that down to what mod it is I can then take a look.

I had the same problem and did some poking around. It looks like it might be The Midnight, but I didn't check to see if any other mods also caused the issue. This is reproducible with just the following:

forge-31.2.0
Reliquary-1.15.2-1.3.4.995.jar
themidnight-0.5.7-3.jar

From messing with the code, it looks like some events might not be firing in the expected order. In particular it looks like this check in onItemRightClick always fails on the client because player.isSwingInProgress is already true: