Eldrazi again

[ELLERfeller]

 {Ulamog, the Infinite Gyre} is hard casted can his ability blow up a  {Teysa, Envoy of Ghosts}?

[Keyeto]

Since Teysa has protection from creatures, Ulamog is unable to target her with his ability. She is safe!

[Keyeto]

Yes, teysa, along with all other creatures are permanents.

Since they are on the battlefield until something destroys them, they are considered permanent.

She has protection from creatures, however, so Ulamog's ability can't target her.

Yeahhhh, i should actually read first before just trying to beat you to an answer huh keyeto?

Sometimes reading helps
Heck, I get excited to answer and jump the gun on reading everything sometimes. It happens to the best of us!
I modified my post so it just answers the question. It's like nothing even happened...

[Gorzo]

You can't beat Keyeto, I swear he has some sort of device that teleports his phone to his hand with the app open when someone makes a post in rules.

[Slenderbro]

You can't beat Keyeto, I swear he has some sort of device that teleports his phone to his hand with the app open when someone makes a post in rules.

I beat him, just with a blatantly wrong answer to the question hahah.

[Mentonin]

Is this ability triggered when he is still on the stack?

[Rigeld]

Yes, because its triggered when he's cast, not when he ETBs.
Which means he's a spell at that time and not a creature, right? (Yes, a creature spell but that's not the same thing as a creature)

[Keyeto]

Alright, I can see where the confusion is here. So let me give you guys a big post with a bunch of rulings!

The relevant rule for protection is this:

702.15b: A permanent or player with protection can't be targeted by spells with the stated quality and can't be targeted by abilities from a source with the stated quality.

Now, what is the source of Ulamog's triggered ability?

112.7.: The source of an ability is the object that generated it. The source of an activated ability on the stack is the object whose ability was activated. The source of a triggered ability (other than a delayed triggered ability) on the stack, or one that has triggered and is waiting to be put on the stack, is the object whose ability triggered. To determine the source of a delayed triggered ability, see rules 603.7d-f.

Relevant part bolded. And just to make sure we're all clear on what an object is:

109.1.: An object is an ability on the stack, a card, a copy of a card, a token, a spell, a permanent, or an emblem.

Now here's where we see that protection still sees Ulamog as a creature source, even while on the stack.

109.2c: If a spell or ability uses a description of an object that includes the word "source," it means a source matching that description -- either a source of an ability or a source of damage -- in any zone. See rule 609.7.

So, protection from creatures means any creatures source cannot harm it. While an object on the stack, Ulamog still retains his characteristics as a "creature" for ability purposes, as shown in the last ruling (109.2c).

RESOLVED

[ELLERfeller]

Thank you because the text on him did not specify he was targeting I was confused and I ended up winning using teysa so I didn't want to be unfair if I was wrong.

[Mentonin]

It does say destroy target creature

[ELLERfeller]

But the text doesn't single out that it's the player or him targeting but my confusion was resolved! Still a noob at magic haha