MISSING LETTERS I

The same letter can be added or inserted at least twice into each of the letters strings below to make familiar words. What is the missing letter, and what are the new words?

LOALT

TRANN

MSTR

 

HINT:

1. ODSSE could be added to the list.

Answers:

 

Two Y's can be added or inserted into each string to form words:

 

LOYALTY

TYRANNY

MYSTERY

(ODYSSEY)