Argthtjtr

If you pick up/hold onto an item before you cast the Blink spell in 5E, will it travel with you to the Ethereal Plane? Would this be possible on successive successful blinks?

I need to get an object out of the reach of an NPC but the player character who has it is currently charmed by the NPC. I hope to grab the item and blink away, but the other player says the item wouldn’t be able to travel with me as it wouldn’t be considered my item.

Any clarification anyone can share on what constitutes an “owned” item (not attuned), particularly in reference to teleporting/blinking, would be much appreciated!

RAW does not specify, RAI clearly yes

The spell only says that you are transported to the Ethereal Plane. Taken strictly and literally, it would mean that you leave all your stuff, including clothes, behind on the plane you start from.

This kind of behaviour would be highly unusual from a D&D 5e spell. You are not expected to account for these things. Spells that transport you are understood to also affect the gear on your person. Some impose limitations, but usually about items that you would not be able to hold.

Also, this concept of "ownership" is absent from the mechanics. You are either holding an item or not. This is in line with the practically expected behaviour of "take even what is bolted down" characterising most adventurers, especially in dungeons.

Ownership has no mechanical effects in 5e.

A thief steals a scroll from an archaeologist who raided it from a king's tomb. Is the scroll owned by the thief, the archaeologist, the dead king, or the country who owns the tomb?

As anyone who has read the final Harry Potter book can attest, ownership can get really tricky. Which is why D&D 5e kept it as far from the rulebooks as humanly possible. As soon as you are holding the item, it is your held item, and is functionally in your inventory.

Now, if you failed to pull it out of the NPC's hands and were in a tug of war with the item when you blinked, I'd say the other player was right as the NPC still held the item. But if you've taken it from the NPC, it's your item.

It's hard to give you a completely accurate answer without knowing the type of item you're asking about nor the nature of its attunement. However, if I were to give a quick compact answer it would be:

Blink can transport the items you are carrying as long as they obey the following conditions: The item is not cursed, is currently within the 5 square block you're occupying and not exceeding twice your height, you are the only one carrying that item, and you're not pushing near the limits of your carrying capacity.

By that, I mean that like Szega said, and as you read, though the spell doesn't mention the items you're carrying or have equipped, it would be odd for the spell not to include them. The only valid reason I could think of as to why the spell is omitting that part has to do with the prior conditions.

Cursed Attunements

Though attunement relates to your ability to wield the item, and not your ability to carry it I do remember a campaign where our druid took the staff belonging to the cult leader we had just vanquished. That staff happened to be cursed and sentient and chose to attune itself to our druid. Though it gave him a few benefits, there were just as many quirks. For instance, due to its sentience, it had the ability to decide what consisted of wielding it and would harm whoever grabbed it even in an attempt to give it to our druid. Another ability it had was to jump into the druid's hand on command from 30 feet away. So for this reason, I'd avoid touching cursed items from your teammates.

Occupying Space and Semi-Control

This, I believe is the most logical and base reason to avoid putting objects in the spell's description. While dealing with an item, there are many players who will try to push the limits on how much you can carry. For instance, say the item in question is a grappling hook you had just hooked onto an eagle. Then are you carrying the eagle? If an enemy has a hold of your spear, then does the half he's holding break off?

Though my numbers are a bit arbitrary, the idea I was pointing out was to say that the only way to avoid such nonsensical arguments is to keep in mind that you must be holding it close to you (so no extended trick with a rope.)

Carrying Capacity

This one is more of a safety net than anything else. The spell states you are taken to an Ethereal Realm and doesn't mention things like time, or if it's the same space. Keeping this in mind, avoiding any chance of dropping the item while in travel would be beneficial.