Tortle fortress V2

From attack after attack, your shell toughened over time providing you the following benefits.

• Your natural armor trait now provides a base AC of 18. As normal, your Dexterity modifier doesn’t affect this number
•  When a creature attempts to hit you with a melee attack you can use your reaction to add your shell defence AC bonus feature plus proficiency bonus to your AC for that attack (base 4 + prof bonus), potentially causing the attack to miss you. You can use this before or after seeing the roll but before the outcome has been decided.  Once you use this ability, you can't use it again until you finish a short or long rest
• If you are subjected to a saving throw or ability check to resist forced movement, you can add your shell defence AC bonus feature to that saving throw or ability check. (base +4)
• When you use your Shell defence feature you can force a creature within 5 feet of you to make strength saving throw DC your AC -2 but before this ability was activated (the DC can not be effected by magical means unless it is lowering it). You must target a creature that is your size class or smaller. On a failed save the creature is knocked prone. A creature that succeeds the saving throw gains a +2 too their next melee attack roll towards you before the end of their next turn. Once this ability succeeds (failed save) you can't use it this way again until the end of your next long rest.