Ulster lock Franco van der Merwe will leave the club at the end of the season to join Cardiff Blues.
Van der Merwe has spent three seasons in Ireland, making 68 appearances for Ulster to date. The South African previously played for the Lions and Sharks.
“We need to add depth in leadership and in that position,” said Blues coach Danny Wilson.
“He has been a fantastic player for Ulster, he knows this competition (PRO12) and he’s played at the top end of the game in terms of achievements in this competition.
“He’s a big leadership figure which in our front five is what we need. (He’s) an on-field presence, but also an off-field and training ground presence for our younger pros.”