What “objects” can a spell target?

Some of the wizard spells have creature or object as the target, e.g. Force Orb [ddi]

What is an object ?

So in the case of Force Orb, could a wizard target say a pebble on the ground, hit it (as it has a very low Reflex) and then hit the monsters around the main target, i.e. the pebble

... this seems a bit of a hack ...

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Can attacks target a square in 4E? (in previous editions this was AC 10) – Snowbody May 4 '12 at 17:17

A pebble is an object. However, D&D4E only provides rules for attacking objects as small as the Tiny size category (i.e. a bottle or book). So if there is an object in a square which is large enough to be targeted by a power then you can target that object and if you hit it you can make your secondary attack against all the targets in squares around it (in the case of Force Orb).

I should also note that the smaller an object is the higher its Reflex defense is. Tiny objects have a Reflex defense of 10 which is the highest for objects (Gargantuan objects have a Reflex defense of 2 for reference). So if a DM wanted to extend the list of available targets to Diminutive targets for example (as a house rule) the objects Reflex defense would be somewhere around 12 to 15 more than likely.

See pages 176 and 177 of the Rules Compendium for all the rules for attacking objects.

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Thanks for the response, and pointer to the pages in the Rules Compendium – SteveC May 4 '12 at 17:16

I don't think the pebble's reflex really even matters here.

The PC is trading the primary target damage (as we assume they don't care how much they hurt said pebble) in order to splash damage targets around them. It seems to be a fairly legitimate and even 'real life' tactic. It's the same thing you do with any other AOE spell - in fact, this only seems to be hurting the PCs, because while the initial attack is 'easier', they're losing the 'primary target' of the spell.

In reference to size categories, it may be worth bringing up semantics on how big the 'force orb' actually is that you are throwing. Maybe the reason why pebble size vs bottle size vs whatever doesn't come into play is because it's irrelevant whether you can target something smaller.

IE - if I throw a basketball at my daughter's toy tree house (roughly the size of the basketball) I hit it. Why would I need to target the dolls inside - if I am able to succeed on the larger target, the smaller one is hit by default because the projectile is too large. Anyway, point is, I'm not familiar with the sizing on Force Orb, but if the 'projectile' orb is too large, it won't matter.

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With the "Target" requirement, the pebble's reflex does matter. A Force Orb spell is not a Fireball spell. Although the two seem to have similar aspects, a Fireball does not have a target requirement, only an area of effect. Thus, the basketball reference, which would fit if this question was about Fireball doesn't necessarily fit with Force Orb. With the target requirement, a new can of worms is opened. If the target is missed, because it is required for the spell, does the spell fail? It may simply dissipate. – Bon Gart May 4 '12 at 18:24
Size categories can produce additional weirdness. My Dm hid a Kenku assassin in a tree, and none of the party could spot it. My wizard threw a force orb at the tree itself, reasoning that anything hiding in it would be considered adjacent. The DM allowed it as it was about the only thing that could work, but what if I'd targeted 'the building' or 'the ship' in later situations? – Ananisapta May 21 '12 at 13:41
@Ananisapta a common house rule, usually invoked when dealing with large creatures, is that the secondary targets must be adjacent to the specific square of the creature or object that's been hit by the power. – Zachiel Sep 15 '12 at 9:07