It's always fun to use the Ethereal Plane to walk right through a party's carefully crafted camp walls!

Just got this as a mount his name is Tedi

I mêan I was about to judge and then realised that I tamed a bulette, so I mean...

Now how did you actually do that?

You don't want to know...

no actually just a bunch of food, charm spells, me playing my lute like a madman, feeding the BBG to him

Our cleric has successfully tied up one and plans on making it a pet. His name will be Darth Plagueis

WISH HIM LUUUCK!!!

I also teared one's legs off and plans on making a poison dispenser.

Does the spider draw an opportunity attack when it leaves the material plane?

No, doesn't leave reach. 

"You can make an opportunity attack when a hostile creature that you can see moves out of your reach. To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach."

Second part: 

You can avoid provoking an opportunity attack by taking the Disengage action. You also don't provoke an opportunity attack when you teleport or when someone or something moves you without using your movement, action, or reaction. For example, you don't provoke an opportunity attack if an explosion hurls you out of a foe's reach or if gravity causes you to fall past an enemy.

So as a DM how do I use Ethereal Jaunt? Can it attack out of it? Can PC's attack it/ see it?

The PCs can't see it unless they can see into the Ethereal Plane, so it also can't be attacked by them. It must shift back into the Material Plane before it can attack.

 Faq: does jaunt provoke an attack of opportunity? No it's the same as misty step in that way. 

Which Chris Perkens made an official ruling on in a Twitter thread. 

Quote from BardsRight >>

It's always fun to use the Ethereal Plane to walk right through a party's carefully crafted camp walls!

 A great example of a evil and clever DM.

Check out the Monsters Know Phase Spider tactics: http://themonstersknow.com/phase-spider-tactics/

Can creatures or objects be pulled through the plane...like if the spider grabbed someone...then moved to the another plane?

I guess it should be able to. But it wouldn't want to (unless instructed by the big bad for example, to imprison PCs) as the spider phases to escape being attacked that turn.

Quote from changwarlord >>

I guess it should be able to. But it wouldn't want to (unless instructed by the big bad for example, to imprison PCs) as the spider phases to escape being attacked that turn.

 Thank you! 

Well if it could do that then the creature would definitely need to be paralyzed of willing, and you would then need to note that a party member is likely to be easily picked off to the ethereal plane and killed so the Cr should be higher, but it technically shouldn't be able to do this at all but it's up do DM interpretation.

And it would DEFINITELY WANT TO DO THAT. 

A player of mine has a vintage wine made of Phase Spider blood

Only the spider can shift into the ethereal plane, not its prey. So the spider can't return there with any prey.