Is it possible to use warlock's Hideous Blow in barbarian's rage?

Question

According to the Complete Arcane book, warlock invocations are not spells. Barbarian rage description in PHB1 says:

While raging, a barbarian cannot use any Charisma-, Dexterity-, or Intelligence-based skills (except for Balance, Escape Artist, Intimidate, and Ride), the Concentration skill, or any abilities that require patience or concentration, nor can he cast spells or activate magic items that require a command word, a spell trigger (such as a wand), or spell completion (such as a scroll) to function. He can use any feat he has except Combat Expertise, item creation feats, and metamagic feats.

So, if invocations are not spells - can I use it in rage? If they are spells can I just multiclass into Rage Mage from Complete Warrior handbook? In the other words invocations are arcane spells or not?

Answer 1

Typically no as warlock invocations are usually spell-like abilities and, as such, require concentration

Warlock invocations like the least invocation hideous blow (Complete Arcane 134) are typically spell-like abilities (CAr 7), and "[u]sing a spell-like ability… works like casting a spell in that it requires concentration…" (Player's Handbook 142).

Because the extraordinary ability rage says that the rager "cannot use… any abilities that require… concentration" (PH 25), the typical creature can't employ any spell-like abilities while raging.

Further, Complete Arcane says, "A warlock cannot qualify for prestige classes with spellcasting level requirements, as he never actually learns to cast spells" (18). The prestige class rage mage has as an entry requirement Special: Able to cast 2nd-level arcane spells (72), meaning that a typical single-classed warlock can't meet that requirement.

Even were the warlock to meet this requirement of the prestige class rage mage by, for instance, multiclassing, the rage magic extraordinary ability spell rage only allows the rage mage to cast spells while in a spell rage, not mentioning the rage mage being able to use spell-like abilities.