Besides being Grimbeorn the Old best friend this card is often very useful and has a few nice target. It can help our old friends Beregond/Beregond to be even more of a stone wall, or power-up it's rightful owner Boromir so that it can take advantage of both the boosts (for other heroes except Grimbeorn some form of external readying is required). Satisfying the condition is usually trivial so the boost will be used almost always.

Absolutely love this card and have 3 copies of it and Gondorian Shield in every Boromir deck I build! —

Such an awesome action advantage card, sort of a limited but not unique Wingfoot. Better in multiplayer of course, where seeing a location each turn is basically assured, but also quite usable in solo with some encounter deck scrying/manipulation. It has some very nice targets, from many Ranger and Lore heroes and characters (Treebeard in high heels anyone?), to more particular Lore characters (like Warden of Healing and Ents for example). One of my favorite cards right now.

An excellent attachment that can be cleared pretty quick if you have some location clearing effects in play. It goes on any hero other than Beorn with no restrictions and thematically works best on in-spirit Frodo who can always soak damage into threat but now can take one less every time. Also good on sentinels, multi-readying heroes like Boromir and softer HP Hobbit allies to help keep them alive.

This card is pricey but it works amazingly in a deck type other than Caldera. Beorn. You can use the great Bear freely to defend as much as you want, soak up archery damage and then when he dies you can actually use this card on him to bring him back to do it again. Best part is if you pair him with Elrond and Vilya then it's free to bring back the bear. Gandalf makes a great third hero but you will want to pack on lots of threat reduction if you go that route.

If you go with Beorn it might be more useful to pack Landroval (and some honor guards) at least they are in sphere. The Houses of Healing might be cheaper in the right deck. Another possibility is to use this event with a Spirit Hobbit and Good Meal. —
I actually run Landroval and Honour Guards in the deck as well. But sooner or later the bear does go down if he is your exclusive combat hero. That's why Fortune or Fate, 3x The white Council, the Will of the West and Dwarven Tomb make up parts of that deck too. —
Here is a sample deck: —

It's been awhile since we got a weapon attachment for tactics. Let's take a minute to compare this one to the current options. Firstly it's nice and cheap at 1, with only the Elven Spear being lower cost.

Dagger of Westernesse is the closest comparison as they both increase a character's attack by 1 for 1 resource cost. Dagger is better if you are running hobbits, low threat or characters that are using ranged or attacking enemies in the staging area as the sword needs enemies to be engaged with you.

Blade of Gondolin is also worth considering as despite the situational attack bonus (a lot of enemies are orc) it also has an incredibly useful ability to help quest while slaying your enemies.

The Elf, Dwarf and Rohan specific weapons are obviously better on their matching species characters and are quite useful.

And comparing the latest three guarded weapons is also a hard one as those weapons are much better but require having to overcome more locations/enemies to acquire them.

The Warrior sword has to be placed appropriately on a Warrior character, but thankfully there are 80+ such options in the game at the moment and this can include allies. The effect is straight forward, +1 attack for each enemy engaged with you up to max of +3. It pairs well with tactics Aragorn and Halbarad who will allow you to engage more enemies. Trap decks also work well to help get and keep the attack bonus at its max. Dale decks are a great way to reuse the cheap weapon to help boost your attacking allies. And characters that can ready also benefit to be able to use the bonus for the whole round. Thematically and appropriately to be art is putting it on Tactics Boromir in addition to his Gondorian Shield and try to engage as many enemies as possible. For the low cost of 2 tactics resources for that combination you could be defending at 4 and hitting at 4-6 which can make short work of most average to low HP enemies.

In closing the Warrior Sword can go on a lot of characters, is a great low cost option for the tactics decks that want to engage lots of enemies and preferably can hit back multiple times in a round. It has a lot of stiff competition and doesn't obsolete any other weapon which is a testament to good design. And if you are Rohan, Dwarf, Hobbit, or Elf there are better options. But all in all it's a great cheap weapon that has a nice fit in the current card pool. And some incredible Boromir art. 7/10