Novaquake Titan is a Unit.
How to Get Edit
Unlike other legendary Sentinels like Sandstorm Titan and Heart of the Vault, Novaquake Titan shouldn't be played as a stand-alone unit and requires a game plan that sees it as a major win condition, or a powerful one at least.
Novaquake Titan's 16-power cost and its 4x requirement make it more difficult to play than most other cards. However, such downsides come with the strongest stats between all other Sentinels and a powerful Bond effect: silencing and putting every enemy unit on the board back into the opponent's hand can punish most strategies that rely on keeping control of the board. This effect can turn any board stall into a sure victory. However, its reliance on having a unit to bond can make it a dead card against strategies that remove your units one by one, and Novaquake Titan's effect is underwhelming against decks that win the game without playing units.
To make the most of Novaquake Titan, play it in a 'tribal' Sentinel deck that plays Relics for the additional card draw from the Bond effect. Stirring Sand can be used to replay Novaquake Titan for just 4 power should it die (however, the Bond won't trigger if it is played this way). Talir's Intervention can save Novaquake Titan from being killed, and allow a second chance to activate the bond effect.
Novaquake Titan goes will with Sentinels with a high attack and low cost to help you bond it sooner, like Refracted Sentinel, Monolith Guardian, Sandstorm Titan, Reality Warden, and Scourstone Sentinel (if you can bond it, at least).
For Relics, Ancient Defenses gives +2 attack to all Sentinels you play, essentially allowing the Bond to discount by 2 additional power. Mysterium Orb synergizes with both your Sentinels any Explorers you play—Sauropod Wrangler can be used to reduce the cost of your large Sentinels, while Seasoned Spelunker is buffed by your Relics and can create a Power Stone so you can play Novaquake Titan earlier.