Discard this card for costs (if you have another Flip monster in your Graveyard), in order to mitigate the cost.
There are two ways to combo this monster with "Spear Cretin". The first is discarding him to bring back "Spear Cretin" and then bring back a high-level monster. The second is using "Spear Cretin" to recycle this monster and destroy a monster.
A deadly combination involving this card would use Brionac, this card and any other Flip monster. It consists of having Night Assailant and your other FLIP monster in your hand, and Brionac in the field. This would allow Brionac to return up to three on the field to their owner hand for basically no cost; in order to make it work, discard your FLIP monster to return any card of your opponent (or even yours, if it matters) to owner's hand; then you discard Night Assailant and its effect will trigger, allowing you to get your discarded FLIP monster back. Discard that FLIP monster again, and you effectively returned to their owner's hand, three cards for almost no cost.
Use "Degenerate Circuit" with this monster to banish your opponent's monsters. It will be a lot harder to take if your opponent is not ready.
Use "Forced Requisition" to make your opponent discard as you discard. This will allow for even more lockdown. As if banishing three cards for almost no cost wasn't enough, you can also make your opponent discard 3 cards.
Use "Calming Magic" to disallow your opponent to make any summon, or "Cold Wave" to disallow them to use any magic/trap card, making this combo a powerful lockdown.