Being inspired by the Sword of Zeus 2.0 I had some ideas about similar items/weapons, all with their unique abilities and trade-offs. The designs and features can be changed and talked about in the Comms team. The image is pretty much self-explanatory, but i will provide a short list below.

Short List:

Trident of Poseidon - a powerfull Trident that provides the holder with an infinite Water Breathing effect. It is enchanted with Mending, Riptide, Impaling, and Loyalty. Consumes Prismarine or Golden Carrots. 

Leathercap of Hades - enables the user to become invisible to any hostile entity in a 100 block radius. Consumes 2 fermented spider eyes for each 5 minutes of use. It is enchanted with Mending and Unbreaking.

Ariadne's Thread - a magical Thread that can be placed in a one way direction and glows in the dark, making finding your way back in a Cave, Mineshaft or in the Nether Fortress quite easier. It does not prevent mobs from spawning and is limited to 270 block length.

Aegis Shield - a powerfull shield, that when held in battle scares hostile mobs away, but gives a Slowness II effect to the bearer. Only has the enchantment of Mending (?).

Toadstone - (also known as Bufonite) , that had the ability to neutralize any poison in existence. Limited to 5 uses only. Consumes 10 levels of XP per use.

Philosopher's Stone - a mythical alchemical substance with the following known abilities:

• to transmute base elements into more precious ones (like Iron to Gold)
• to prolong a persons life span (prevent death like a totem?)

As this is a very overpowered mythical item, it requires equally powerfull drawbacks (since it is an alchemical object the drawbacks can easily be attributed to the law of equivalent exchange, namely "You cannot gain anything without first giving something in return. To obtain, something of equal value must be lost."), i propose to set in place different drawbacks for each one of the two different types of usage. For example, using it to transmute objects consumes a large sum of the base object, using it to prolong the life spawn consumes large amounts of xp.

Thank you very much for giving us the chance to express our ideas!

Personal Opinions:

Trident of Poseidon - Perhaps it gives a new charge of Water Breating every time you use Riptide? Consumes the item on Riptide use as well, which hopefully makes it very easy to code.

Leathercap of Hades - Considering the render distance, that's basically just invisibility. Otherwise, it seems interesting. I imagine this as something you use in the dark to cloak yourself inside the darkness. Perhaps it only works in certain light levels? 

Ariadne's Thread - no real comments here. sounds interesting, but i think i don't full grasp how it works. sounds like breadcrumbs.

Aegis Shield - It would be interesting if it had a higher level of thorns, so you basically become a slow, walking mirror shield. Scaring mobs away as a passive would be interesting and could have issues depending on how often mob AI is evaluated due to server plugins.

Toadstone - Since it consumes levels of XP, I honestly don't see why it can't be used forever. 

Philosopher's Stone - Idk about changing items (sounds like it'd be better as a cool anvil or crafting table), but i like the "prolong a person's life span". Perhaps something as simple as "When held in the offhand slot, if a player would die, check their current level. If above 30, remove half of them, rounded up, grant the effect of a Totem of Undying, and return the Philosopher's Stone to their offhand." 
Makes it hard to stack it forever (1 use at level 30, 2 at 60, 3 at 120, 4 at 240 etc.) without having to spend a LOT of time grinding. Gives a better reason to keep those levels too. 

Personally, I very much like the concept of being able to consume XP as a resource. XP Farms would have more use than just tool repairs and the absurd amount of levels from voting could be put to use. Since enchanting tables aren't needed much anymore due to villager trading mechanics, having scaling uses like the Toadstone and Philosopher's Stone would be great additions :)

Exactly, i was thinking that xp is not very appreciated by many players, so that would give them a better use for it. Basically all of the items/tools could be xp powered. I've noticed that players are rather dissapointed when only getting xp after a dungeon run so, that would make it a lot more precious as a resource.

And yes, i suppose that the Toadstone and Philosopher's stone would be the most interesting ones to be added. 

About the changing items, the Transmutation process is more of a get-out-of-trouble mechanic, in a sense that, if you really need a specific element, but there's none of it in the vicinity, you could transmute a base element that is available. Obviously this sounds like it would make finding said resources obsolete, so the coungter balance needs tobe very high. For example, if you really need a block of emerald/gold you could transmute it from iron or lapis or redstone. And this could not be done to organic matter, as organic tranmutation was considered impossible and/or forbidden. Maybe to do that it would consume the amount of xp you refered to, plus some of your health.

XP needs to become more valuable. I believe these additions can add to it's value.

P.S. I was reading all the the other Ideas/Feedback of the year and i noticed that the Poseidon Trident has already been suggested by Colonel_Gagne, so props to him for coming up with it earlier!

Hey Black,

I know you were in our meeting :>, but I want to officially respond to it and say we really liked these ideas, and think with a bit more consideration and balancing are something we hope to get in the game!

- Community team

I don't know if I'm misunderstanding what exactly the toadstone does, but I'm pretty sure if you want to neutralize poison you can just use milk, right?