Husk

 is a cheap defensive unit  with low Health and Prompt.

Strategy
 is a flexible defender that costs the same amount of gold as Engineer for the same amount of defense but has Prompt.

While being strictly inferior to an Engineer when considering cost for Health, it is useful in random sets containing high cost red units such as Lucina Spinos or Tatsu Nullifier: these units often require having 2 Animus in play for a total of 4 produced every turn, most of which would usually get wasted as soon as you enter the mid/late game where your gold has to go towards buying defense. provides a sink for this otherwise wasted and lets you improvise your defense more easily with its Prompt.

is also great for improving your defensive granularity without delay if you realize your opponent might try to finesse your defense next turn.