Champion

Effect

Once per game, permanently grant +8.5% attack speed and damage reduction to a fighter

Very strong on Soul Gate and its upgrade Hell Gate due to being able to let out an extra spawn while also buffing all spawns before wave 10.
Strong synergy with any healing such as Seadragon and Desert Pilgrim due to getting extra value from each heal.
If you are scared of leaking on wave 1 to a snail, you can immediately put it on your vulnerable opener such as Gateguard and Windhawk in order to leak less or even hold snails on wave 1 or 2.
Stacks additively with hyper carry units such as Doppelganger and Dread Knight if you ensure that these units would be the last ones left alive on your board.