If this isn't my favorite location control card, it's pretty close. Sure, it doesn't put progress on locations like a Northern Tracker, Asfaloth, or other similar cards. However, has a lot of other things going for it:

First, it is in Leadership, whereas most location control is in Lore or Spirit. This makes it available to decks that otherwise wouldn't be able to include location control at all.

Second, it is inexpensive. It is easy to get out early even in multisphere decks (unlike Northern Tracker or its ilk). It does cost you a character action, but there are plenty of characters that don't do that much after coming into play. Great targets include Snowbourn Scout, Herald of Anórien or an extra Errand-rider.

Third, encounter decks don't tech against it very much. There are plenty of quest cards and locations that prevent direct progress on staging area locations. Other than cards that are straight up immune to player card effects, cards don't tend to hinder this effect.

Fourth, it is useful in almost every quest. There are always locations that you would rather not see, whether it is because of high threat, bad travel effects, bad while in play effects or otherwise. This allows you to get them out of staging and replaced with something easier.

Fifth, it is absolutely great tech against certain quests. This at least makes this worth of a side board spot in decks. This card really shines in any quest that puts tokens on locations -- whether that's damage in Celebrimbor's Secret or Raid on the Grey Havens, time counters in The Antlered Crown or mire tokens in The Passage of the Marshes. In all these quests, the tokens are time bombs waiting to go off and cause bad effects, and Mariner's Compass can reset the timer on a location. Also, it can free up guarded cards from locations in any quest that has them (or for any player deck that runs them).

This isn't a review but a question: If I play this card with a nearly empty encounter deck so no treachery is revealed, I assume I will not get the readying. However, the questing boost seems to be a separate effect. Will it still trigger?

There was someone who said that Galadriel's effect could be activated with the put into play effect of this card because of 'put into play from his hand'. But, I think Galadriel's effect will not be activated unless 'enter' because 'put' must be distinguished from 'play'. Which one is right?

At first glance, one might think: “What?! ALeP gave Tactics its own Unexpected Courage? And at exactly the same cost? OP!” At a second glance, however, comes the realization that this is an encounter action, which makes it much more tricky to use. So, what is this card good for? Well, firstly, it is reliable action advantage for Tactics, and having a Warrior hero in that sphere is not that unlikely. So, you could use it on a questing hero with good combat stats, enabling them to contribute to both, but finding a suitable questing hero with the Warrior trait isn’t as easy as you might think (especially in a tactics deck, which this card seems to be made for); and Théoden already has his own action advantage in Snowmane, although that is off-sphere, so this can be a good alternative if you don’t play spirit. Glorfindel comes to my mind as a good option if you’re running a Tactics-Lore deck so that his bloated stats are not wasted, and of course the new Glorfindel released in the same pack with Onward into Battle (he just loves tailor-made attachments, doesn't he?). Then, there are the Siege and Battle quests, where this card can be extremely useful. The problem with those keywords is that your heroes (and allies) have to do double duty with their combat stats, so the characters you send for questing are also the ones you want to manage combat with, resulting in those unfortunate moments where you have to decide whether to lose because Beregond has to defend and thus cannot quest, or because he was questing and thus couldn’t defend. Onward into Battle helps with these quests, so that’s nice; but outside the Against the Shadow cycle and some rarer occurences of the keywords, situations where you want to quest with your Warriors are few and far between. So, what else is this card good for? Well, this card makes sure that combat heroes will be available for combat. That may sound a bit strange, since there are no obvious reasons why they shouldn’t be seeing as they did not quest (and there are no Warrior heroes with self-exhausting abilities that I remember). But very often, one can find themselves in a situation where their combat hero had to be exhausted prior to the combat phase. To give a few examples:

• An enemy made an attack outside of the combat phase (a classic!). This can often throw your most careful plans out of the window, as those enemies are often already nasty ones you want to defend with your big hero defender; but then, this defender will usually be unavailable to defend a regular attack. Think about the many enemies making an immediate attack after they have engaged you. With Onward into Battle, your defender will be able to defend both their attacks.
• You made an attack outside of the combat phase. Arguably less common, but still a grat use case for this card. Quick Strike and Hands Upon the Bow are classic examples of cards allowing you to make an attack outside of the normal framework. Since both these cards require a single character to attack, that means it will often be a beefed up attacker like Legolas. Now, killing an enemy without having to defend it first is great in and of itself, but it’s even greater if you can ready your big attack guy and deal with another enemy the normal way.
• Shadow insurance. There’s one shadow effect that has been popping up more and more in the later cycles. “Shadow: Defending character cannot ready until the end of the round.” This can be really problematic, because that means your defender won’t ready in the refresh phase, so you won’t be able to use him in the next round. That often means having to chump or take an attack undefended, which can be harmful to your board state. But with Onward into Battle, your defender will be up and running again once the encounter phase comes.
• Various sporadic uses. Action advantage is always useful for travel effects requiring you to exhaust a hero, and Onward into Battle is no exception. It is also great for the racing tests in Challenge of the Wainriders, so that the hero with the big numbers in the of or department can do the test and will still be able to fight. Also good for sailing tests, because when sailing, ever body is needed.

All these cases are helped by Onward into Battle, which makes it a very versatile addition to the card pool, and it’s also a very fun card to find various uses for. It is not an Unexpected Courage clad in red, but that’s a good thing in my book. Nevertheless, it can often make your life that crucial bit easier. Give it a try in your tactics deck, and you most likely won’t be disappointed to draw it!

TL;DR: This is 100% a "build-around" card, but if you do build around it, it's incredible.

I usually don't like temporary stat-boosting cards unless they have the potential to make a big impact. Scouting Party is that 100%, but it isn't something that you can just throw into any deck - you really have to build around it, which is why I never used it at first. But it so happened that one day I noticed that I had two Scout heroes in my collection that I hadn't used yet (Idraen and Lanwyn), so I decided to make a Scout deck and give it a go. (Edit: You can find the deck here.)

While building this deck, I kept thinking that this card is more restrictive than it looks! It turns out that out of a lot of the questing allies that I usually like to use, such as West Road Traveller, aren't actually Scouts. But I took this as an opportunity to dig even further into my collection and pull out things like Sailor of Lune and Mirkwood Explorer that I also rarely use or have never used before.

The first quests I played with this deck were The Caves of Nibin-dûm and the first two Dream-chaser quests in a 2-player fellowship. And every time Scouting Party came up in the game, it made a HUGE impact - it ended up boosting my by 10 or more every time I played it! It's balanced pretty well - it's restrictive to play it, but if you build your deck around it, it's incredible.

However, like most other temporary stat-boosting events, there were a lot of times where my stats were already good enough that I simply didn't feel like I needed it. Though to be fair, the other deck in the fellowship was playing Prince Imrahil with A Very Good Tale and Captain's Wisdom and was spewing out allies left and right, so that might not be this card's problem, lol.

Also one thing to note: This card is obviously best when you go as all-in as possible with your questing. This is not a bad thing, but this factor alone makes the card much better in multiplayer than in solo, because then you can go all-in with your questing while the other players handle the combat. One of the reasons that made me not use this card for a while was the fact that I play true solo about 60% of the time.