How do I control a 12V relay with a 1.8V microchip?
You could use a BJT + MOSFET or a very low Vth MOSFET.
An example of the latter would be the SQA410, which will dissipate less than 1/4W when on.



simulate this circuit &ndash; Schematic created using CircuitLab
The 2A Schottky diode protects the MOSFET from the inductive kick when the coil is turned off. R1 is to ensure the MOSFET is off (and not partially on) if the MCU output is floating. R2 provides some measure of protection against ground bounce.