On Asgard Ascension, the follow client modifications are whitelisted, meaning you may use them freely:
5Zig, LabyMod and similar client add-ons
Armor, status effect and potion HUDs
Too Many Items, Not Enough Items and other item-browsing modifications
All texture packs excluding forms of x-ray
Schematic modifications excluding the printer function
The use of any modifications not listed above is not allowed and will result in punishments if you are caught. If you are unsure whether your mod can be used on Asgard Ascension, please ask a staff member.