Can powers that grant a basic attack, like many of the Warlord powers, be used to grant an attack to a summoned creature? If so, what does the summoned creature use for its basic attack?
Inspired by Conjuration, Summoning, Pet rules?
The summoned creature is a valid target of such effects however it has no inherent ability to use basic attacks so the end result is not favorable for you.
The attacks allowed to each summoned creature are as listed for each power. Currently I am aware of none that grant basic attacks. Summoned creatures are not granted any basic attacks by default. Basic attacks are indicated like this for Melee basic attacks and like this for Ranged basic attacks.
The Rules Compendium states on p120 in the Commanding the Creature section that, "The Summoned Creature has no actions of its own...The Summoning power determines the special commands that the summoned creature can receive and gives an action type for each command."
Compare Basic Attacks to Opportunity Attacks.
Opportunity Attacks, like Basic Attacks (as Simon notes) are also granted to all creatures (RC p246). There are many summoned creatures that are explicitly granted Opportunity attacks. See Phantasmist Stalker for one example, its Opportunity Attack is identical to its normal attack.
From this you can infer that Summoned Creatures do not have Opportunity Attacks by default. Hence they should have no Basic Attacks as well.
As I read Dragons#385, pg54, it talks about intrinsic nature, with respect to the summoned monsters in that particular book. Also, looking at the 'Summon Dretch' It states that this monster, if left uncommanded, attacks or charges, and uses it's listed attack in place of a melee basic attack.
This brings about the notion that a summon monster can charge, which is a basic attack. Furthermore, from reading the monster manual, there are a lot of monster that do not have opportunity attacks listed, but it is assumed that they can preform such basic actions.
It is true that a summoned creature has no action on it's own but a Warlord's Direct the Strike, gives the ally an action. Besides the rules for Basic Attacks clearly states that these are At-Will's that everyone can use regardless of class.
The only issue I see if that the monster would have to make that attack through the caster's strength (for melee basic).
Comparing Basic Attack to Opportunity Attacks: There are a few Artificer summons that list opportunity attacks. I would argue that those opportunity attacks are not basic attacks. The opportunity attacks listed for summoned monsters have added effects such as Marking or to ensure that the Artificer uses Intelligence instead of Strength for opportunity attacks.
If a Power lists target as ally then yes, as summoned creatures count as allies.
If the power lists creature as target then yes, as summoned creatures count.
In the definition of Basic Attack in the Rules Compendium (p238-239), it indicates that basic attacks are powers that everyone can use, though it is possible to read that sentence as applying only to player characters. Later in the definition the RC states that effects can allow creatures to make basic attacks, and unless they have a power that counts as a basic attack they make Melee Basic Attacks or Ranged Basic Attacks.
I would interpret this to mean that a creature lacking it's own basic attack power, can use the core basic attack powers, and so a summoned creature granted a basic attack could use the standard ones.
As for what stats do they use? Page 121 of the RC indicates that the summoner makes the check using the summoner's game statistics (but without temporary bonuses or penalties).
So the warlord grants a basic attack to the druid's fierce boar, the druid can make a Str vs AC, [W] + Str damage melee attack for the boar.
And still we have to wonder what damage dice to use if the attack hits.
The best I can answer there, is that you should either treat the attack as unarmed, and do d4 damage, or use the damage dice normally used by the summoned creature, in this example d8. I don't see rules supporting either, so I would suggest it's up to the DM
Actually, summons by virtue of not being actual creatures but rather pseudo-creatures that must be given special commands to do anything, I don't think would benefit from the warlord's business. Its not that they can't have basic attacks, but rather they cannot take an action without being commanded to do so (unless specifically written on the power).
It goes something along the lines of - Commanding the creature: The summoned creature has no actions of its own. You spend actions to control it. But I do not have the page reference or full text, regardless the question should be answered by the summoning keyword or the power proper, not by whimsy extrapolation.