Trjtdtk

I'm querying an effect which specifically removes creatures from combat altogether such as Reconnaissance or Spires of Orazca.

If the only attacking creature is removed from combat by an effect like this, how does this attack or lack thereof interact with things like the Raid mechanic and Curious Obsession?

Does it check "Was an attack initiated at all?" this turn or "Was an attack "successfully" made"? Does an effect like the above "prevent" an attack?

I wondered this since burning the creature at any point after it has already been declared as an attacker still makes it count for "a creature attacked this turn".

Declaring a creature as an attacker is a singular event that is not undone by later removing that creature from combat. For example, you will get the benefits of Raid and you will not have to sacrifice Curious Obsession in a turn during which all of your at least 1 attackers have been removed from combat.

Note that effects like that of Spires of Orazca are not the only ways to remove a creature from combat. Simply destroying or exiling a creature also remove it from combat.

506.4. A permanent is removed from combat if it leaves the battlefield, if its controller changes, if it phases out, if an effect specifically removes it from combat, if it's a planeswalker that's being attacked and stops being a planeswalker, or if it's an attacking or blocking creature that regenerates (see rule 701.14) or stops being a creature. A creature that's removed from combat stops being an attacking, blocking, blocked, and/or unblocked creature. A planeswalker that's removed from combat stops being attacked.

Effects like Raid or the 2nd ability of Curious Obsession do not care whether or not the attacking creature(s) were in combat the whole time, or that they dealt combat damage, or anything else. All that matters is that you have successfully declared at least one creature as an attacker this turn.

508. Declare Attackers Step

[..]

508.1m Any abilities that trigger on attackers being declared trigger.

Note that there are effects that put a creature onto the battlefield "tapped and attacking". Creatures that have been put onto the battlefield this way do count as attacking creatures, but do not count as having been declared as attackers. In practice this doesn't matter for Raid or Curious Obsession because all those effects have a prerequisite of an already attacking creature, which would already satisfy Raid and CO. But it would matter for abilities that require a certain number of creatures to have been declared as attackers, such as Windbrisk Heights

I couldn't find a definitive answer in the Comprehensive Rules, but the post explaining the mechanics from the Ixalan set says:

Raid abilities also don't care about what happened to the attacking creature. Maybe it survived combat, maybe it didn't. Maybe it got bounced. Maybe it changed controllers (that traitor!). As long as you attacked with it, that's good enough for a raid ability.

I would think that bouncing (returning the creature to its owner's hand) would be comparable to the ability on Reconnaissance or Spires of Orazca, so this situation would count as "a creature attacked this turn".

Abilities like Raid check if an attack was declared. This means that if a creature is removed from combat in any way after being declared as attacking, it will still meet the conditions for raid. Creatures can be removed from combat in many ways, cards like Maze of Ith and Reconnaissance will untap and remove it, the creature can change controllers because of cards like Word of Seizing or Act of Aggression and no longer be attacking, or the creature could leave the battlefield, by being dealt lethal damage (Lightning Bolt), sacrificed (Celestial Flare), destroyed (Doom Blade), bounced to the hand (Unsummon) or exiled temporarily (Ghostly Flicker) or permanently (Unmake).

Note that it's declaring a creature as attacking that meets these conditions. If a creature attacks without being declared as attacking, say when Meandering Towershell returns tapped and attacking a turn after his attack was declared, it will not meet Raid's conditions, this is also why it doesn't meet it's own conditions and exile itself every turn. This is however the only thing I can think of that will be attacking when no attacks were declared, all other abilities that put creatures into play tapped and attacking require something to be declared as attacking already like Hero of Bladehold.