Abilities are recieved as nether stars, which you eat to apply.
There's 3 ability slots, the primary slot, and two secondary slots.
To withdraw abilities, you can use /withdraw SLOT
When you die, you lose one random ability.
Upgraders
Upgraders are items which transform your ability into an ultimate.
There's only one of each ultimate; if someone got it before you, you wont be able to use the ability
You use them by eating them while having the ability equipped.
Not every ability has an ultimate, and by extension, not every ability has an upgrader.
End
Killing the ender dragon will give you strength 3 for 10 minutes.
The dragon egg may or may not be used for something.
Mace
You can't get the mace through the crafting recipe. It will be obtainable through an event.