Radiant's Last Stand1WW Enchantment — Saga
• You gain 7 life.
• Tap target creature. It doesn't untap during it's controller's next two untaps steps.
• Choose a white Aura you own from outside the game that enchants a permanent and attach it to any permanent it can enchant.
Intrepid Hero's Resolve1W Enchantment
As Intrepid Hero's Resolve enters the battlefield, you choose +1/+0 or +0/+1.
Creature you control get the chosen power or toughness increase.
Creatures with entangler may block creatures as though they have no abilities. "An army of one is very real. I've seen it. It made me taste the bitterness of defeat—and all my pride was laid to rest with my retreat."
For those unaware, entangler is one of the first concepts I keyworded when I began developing Magic.
It is a throwback to Entangler and does exactly the same thing.
I'm going to assume your Saga is a standard 1, 2, 3. Since you didn't put anything else. That last ability is far too powerful as Dumplings said. Without restricting it in any way this has to cost a minimum of 2 more and possibly even more than that. If you limit what it can grab so nothing dangerous occurs then the cost could stay the same. As for wording. You just put the aura into play. The rules already do the rest by design.
The buff is small enough for an extra ability but without knowledge of entangler and how prevelant it would be its hard to say how good it is.
Angel's Mercy is also a completely garbage card and Lone Missionary exists and is more abusable as a creature. Gains more than half the amount of life and costs half the mana. Birth of Meletis also exists as does timely reinforcements. 7 may be a tiny bit high but it's definitely not implausible.