Clash of Clans – How to Use Santa’s Surprise Spell Effectively

Rage spell will increase all troops'es damage and heal, it just won't affect on other spells.

From wiki :

The Rage Spell creates a translucent purple ring on the battlefield that boosts the movement speed and damage of any friendly units inside the ring. In the case of Healers, the Rage Spell increases their healing by a similar amount.

For test you can send a level 5 wall breaker toward some level 7 walls, he will destroy the wall with rage spell but he can't destroy it without the spell.

It is a bit weird at first - the destruction of your base only yields a hunk of your resources being stolen. Repairing your base takes only a few seconds and costs very little.

The overall goal in the game is pretty murky. There are ever-increasing base upgrade goals to be met, which you will gain either by waiting for your own resources to collect, or more quickly by raiding other people's bases. Pride in your town's strength and building levels could thus be considered a major goal of the game.

However, I would argue that the overall goal is to rank highly in the player-vs-player leagues, which require you to amass tons of trophies by successfully attacking other bases or defending your own.