If you Smite it you get health back. If you deal the killing blow to it you get Crest of Cinders from it.

Using Smite on the Red Brambleback

Using Smite on the Red Brambleback will restore a large amount of health instantly (20% of your maximum health). This bonus can only be claimed once per spawn.

The Red Brambleback gives off green bubbles if the Smite bonus is available. Once the bonus is harvested, the effect disappears until the Red Brambleback respawns. This is only visible to champions with Smite.

Gaining health by smiting the Red Brambleback is... Read More

5.7 Patch Notes: Items

5.7 Patch Notes: Gift of the Toadstool

Decided to revist the numbers on this in light of the changes Riot made to Enchantment: Cinderhulk and Gift of the Toadstool in Patch 5.7.

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Using Smite on the Greater Murk Wolf will summon a nature spirit that grants sight over the nearby crossroads for 75 seconds. Whenever an enemy champion comes in range of the nature spirit, it will chase them for a short duration. This bonus can only be claimed once per spawn.

Additionally:

It actually also pings and throws up a flag on the mini-map when it has spotted an enemy, though I've observed this can get lost in the bustle of a 5 on 5 Summoner's Rift game.

It will not detect stealthed enemies.

Usage:

Vision is useful so this ward is... Read More

Using Smite upon the Ancient Krug will grant you Gift of Heavy Hands for 90 seconds, causing every 6th basic attack to stun minions and monsters. Additionally, you can attack a tower to expend the buff early - dealing a large amount of bonus true damage (65 + 15 x level). This bonus can only be claimed once per spawn, and only by smiting the Ancient Krug - Smite cannot be used on the small Krug.

Usage:

First 1-2 jungle clears for autoattack based jungle champions, which often includes even tanks like Nautilus who typically run Attack Speed Marks if not... Read More