Rabbit

Token Upgrade
You can use a pet token to improve certain stats Rabbit receives from Earth elemental equipment. Each piece of earth gear will give Rabbit an increase to base speed of 5% * equipment tier. So a single tier 3 earth equip would give a 15% boost to Rabbit's speed, and three tier 3 equips give Rabbit a 45% increase to base speed. This speed increase also applies to any wind gems slotted into the earth gear, so a tier 3 equip with a level 10 wind gem would get an additional 34.5% speed, instead of the standard 30%.

In addition to this increase in base speed, Rabbit also receives a flat +50% bonus to attack from all Earth equipment. This bonus also applies to all fire gems slotted into the equipment, so a level 10 fire gem on a T3 earth equip would give an additional 45% attack instead of the standard 30%.

TL;DR: Improving Rabbit is really good. Just give him your best earth gear with three fire gems.

Below is the same Rabbit before(left) and after(right) the token Improvement.