We can agree to disagree, sure, but one of us is wrong and it is not me.

The Ugin spell does not target, it's as simple as that. It cannot have targets. If it had a target, that target would have to be chosen when the spell is cast, before costs are calculated and paid. Casting him triggers an ability, which is its own object on the stack, and that ability has a target. Triggered abilities, and activated abilities, are their own thing, their own objects with their own characteristics. When an ability is put on the stack, if it requires targets, those targets are chosen when it is put on the stack, just like spells as outlined in rule 603. Most importantly, they are independent of their sources.

Arena handles this correctly. You have been educated on how it works, and why, wether you accept it or not. But perpetuating this now in paper Magic means, that you are knowingly cheating if you try to pull this in an event. Or you get a (not so big) surprise when your opponent calls a judge on you and they rule against you (correctly). What's more worrysome, is that your false thinking may make other players also play this wrong, and then they get called a judge against them and get a bad surprise.

@Rezzahan. I wasn't saying you're wrong about Tectonic Giant. We disagree sure. Personally I think all cards are spells until they hit the board. But you that does prove you have to be wrong about one of them.

Either you were incorrect in saying if you had a card that said "the next time you cast a black spell destroy target permanent" OR. You're wrong about Ugin being able to target Tectonic while still being a spell.

I wouldn't even question it if Ugin used his passive to exile my card by casting a colorless. However his effect comes in two parts.

One static from casting self and one triggered from casting others.

Magic has a lot of self checks.

It would be a lot easier to say the instant example was wrong because it would check the source and see it was a spell.

No, it doesn't. The issue is, that you mistake the SOURCE of the ability for the ability itself. Things like protection and hexproof from a color look at the source of an ability to see if they apply. Tectonic Giant doesn't care about the source of an ability, it doesn't care about abilities at all. It looks at the thing that targets it, which is an ability, and therefore doesn't trigger, because an ability is not a spell.

@Rezzhan.

603.7d If a spell creates a delayed triggered ability, the source of that delayed triggered ability is that spell. The controller of that delayed triggered ability is the player who controlled that spell as it resolved.

Mtg wiki disagrees with you

And here's another rule, you want to read.

603.3. Once an ability has triggered, its controller puts it on the stack as an object that’s not a card the
next time a player would receive priority. See rule 117, “Timing and Priority.” The ability becomes
the topmost object on the stack. It has the text of the ability that created it, and no other
characteristics. It remains on the stack until it’s countered, it resolves, a rule causes it to be removed
from the stack, or an effect moves it elsewhere.

"@Razzahan. So you believe if you had an instant that said "the next time you cast a black spell destroy target permanent" it wouldn't be the target of a spell because it's a casting trigger spell."

Correct, though I do not believe it, I KNOW IT FOR A FACT. That spell would set up a delayed triggered ability, and if triggered, that ability targets, not the spell that triggers it, nor the spell that set up the delayed trigger.

"Triggered abilities are attached to permanents that are already on the battlefield [...]"

For that claim you have to give a citation. But you won't find any, because it's not in the Comprehensive Rules. How the CR define triggered abilities I quoted earlier already. You are too hung up on your false conviction, that it has to be a permanent that has the triggered ability. No. ANY object can have triggered abilities. Cards in the graveyard, cards in exile, cards in the LIBRARY, cards in HAND, and spells on the stack. Heck even EMBLEMS in the command zone.

"My problem is that Ugin targets him before he enters. He doesn't even need to enter. Not sure how it can be said Ugin can target Tectonic, not being a permanent and then still say it wasn't the spell that targeted it. Ugin doesn't exist yet."

Ugin DOESN'T target as a spell. He CANNOT target as a spell, because he is not an aura spell, nor cast via mutate, which are the ONLY kind of permanent spells, that CAN have targets. Ugin is merely the SOURCE of the ability, but it is the ability itself, that does all the things. Ugin, being on the stack or not, being on the battlefield or not, is irrelevant.

"Those decks are built off casting triggers not triggered abilities."

What do you think a casting TRIGGER is, if not a TRIGGERED ABILITY?

@Razzahan. So you believe if you had an instant that said "the next time you cast a black spell destroy target permanent" it wouldn't be the target of a spell because it's a casting trigger spell

@Rezzahan. Those decks are built off casting triggers not triggered abilities. Triggered abilities are attached to permanents that are already on the battlefield like Hullbreaker Kraken for example. (Whenever you cast a spell) but Hullbreaker needs to exist as a permanent and not on still be on the stack or be between the steps of being a resolved item and a permanent. If Tectonic was the target of Hullbreaker you'd say it's a triggered ability. My problem is that Ugin targets him before he enters. He doesn't even need to enter. Not sure how it can be said Ugin can target Tectonic, not being a permanent and then still say it wasn't the spell that targeted it. Ugin doesn't exist yet.

No one said anything about Tectonic Giant becoming the target of the Ugin PERMANENT. He becomes the target of the TRIGGERED ability of a spell on the stack. The target of an ABILITY. Permanent spells can only have targets if they are aura spells or are cast via the mutate ability. The triggered ability, like any other cast trigger, resolves BEFORE the Ugin spell, not afterwards.

Addionally there's the distinction between enters the battlefield and cast-triggers. Even if Ugin is countered it will still trigger allowing you to target something. He'll never enter the battlefield as a permanent but Tectonic would still be targeted by Ugin after spell step resolves. Still making Tectonic the target of a spell and not the target of a permanents ability.

Whereever it says that a nonpermanent cannot have triggered abilities is so wrong it cannot even be described. How do you think cards like Arclight Phoenix, Bloodfeather Phoenix, all kinds of other Phoenixes, the whole host of flashback cards, exhume cards, any other graveyard based activated or triggered cards, freaking STORM cards, replicate cards, conspire cards, etc. are supposed to work? None of them are permanents when they are triggered or activated.

Here's the storm example, straight from the Comprehensive Rules:

702.40. Storm
702.40a Storm is a triggered ability that functions on the stack. “Storm” means “When you cast this
spell, copy it for each other spell that was cast before it this turn. If the spell has any targets, you
may choose new targets for any of the copies.”

And another thing: The Ugin spell is the SOURCE of the ability, but it is the ability itself that targets, not the Ugin spell.

@Rezzahan. Yeah it's making even less sense to me after digging deeper. It says non permanents cannot have triggered abilities. Ugins ability takes place before he's even in play as a permanent and only activates when he's successfully cast. Which would make him a resolved object and not a permanent during that step. The same step Ugin targets Tectonic Giant still being a spell.

100% certainty and then some if that were possible:

113.3c Triggered abilities have a trigger condition and an effect. They are written as

“[Trigger condition], [effect],”

and include (and usually begin with) the word

“when,”

“whenever,” or “at.” Whenever the trigger event occurs, the ability is put on the stack the next time a player would receive priority and stays there until it’s countered, it resolves, or it otherwise leaves the
stack. See rule 603, “Handling Triggered Abilities.”

And now look at Ugin, Eye of the Storm:

"WHEN you cast this spell, [=trigger condition]

exile up to one target permanent that's one or more colors. [=effect]"

You should also have noticed when Ugin was cast, there was a seond object put on the stack above it right away by Arena, with a target, which means, the Ugin spell, and that second object are different things.

@Rezzahan. How sure are you about that? The text reads "when you cast this spell exile up to one target permanent" meaning before it even enters and becomes a plainswalker. Making it the target of the spell itself.

Tectonic Giant doesn't trigger because it is targeted by an ABILITY. It can only trigger when targeted by a SPELL. A cast trigger, like Ugin has, is still triggered ability, even if it is triggered by casting the spell.